The fact that they have no special genetics traits/benefits/flaws is what makes them special on their own. They are the ideal Space Marines, pure in mind and body.
I personally believe that each chapter represents aspects of humanity itself. The Ultramarine represents humans desire for structure and discipline, and like every other chapter there are goods and bads to their philosophy.

There is something that have not been mentioned yet about the Ultramarines that is very unique to them.
Rather than "only" controlling a single planet/"insert equivalent" they control nine starsystems. They are basically their own Empire. If that does not count for something than I don't know what.

This sentiment--although appreciable--ironically reinforces the backlash against Ultramarines. With the setting being so "Grimdark"; the Ultramarines come across as "Mary Sues" or as "unapologetic ubermenchen" due to the fact that they are nigh-blameless/unblemished. Although one could argue that this is the very reason to laud them.
[A similar reason is why I love Orks so much: all this Grimdark needs some comic relief!]

What many of us don't see (and this is Games Workshop's & Black Library's fault) is that there's very little "bad" attributed to the the Ultramarines' attributes/philosophy/actions--in canon. We, as snarky fans, point out the inherent flaws in the Ultramarines being "walking paragons" and "foolishly adherent to the Codex Astartes" and "Generic" that we call the legion derogative names (Smurfs and what have you).
[My personal favorite is a jibe against the primarch's name: "Rawbutt Girlyman" ^_^;;]

Now THERE'S something I'd like to discuss/debate:
In Know No Fear there are chaotic/rebellious insurgents among the Ultramar domain; but (I'll kindly chalk up as "oversight") there are little-to-no reasons as to why there are humans within the Ultramar system willing to seek alternatives/Chaos. The closest you get in the aforementioned novel is "Intellectual Curiosity".

IF, the narrative/canon would have gone into how a significant portion of the Ultramar population balks against such an absolute, draconian authority (much like the actual "imperfect" Rome, or against an analogous 1984's "Big Brother"), THEN I would have a basis on liking the Ultramarines.

In other words: the Ultramarines would be so perfect that many of their territories/planets can't stand the yoke of unerring/absolute rule--as it were. That is the most delicious irony, and my sympathies would go with it.

We charge admission to gawk at our Primarch. We win!

Dakka, it's part of the Imperium. It's only apparently perfect because just about everywhere else is constantly a warzone, polluted to the point of being barely habitable, enslaves its own populations to produce machines of war, is ruled by a scarily dogmatic religion of fanatics, is being invaded by orks or is a daemon world. That might be generalising a bit, but as a rule the society is not dominated by the same crushing despair or failings of many others.

Reading your post, I get the distinct feeling you have read little beyond Know No Fear or the codices about the Ultramarines nor taken a look at what other authors have produced. As such allow me to make this clear: They do have failings when given to the right author and they do have interesting traits.

Fall of Damnos was a decent book (despite the SPESS TOMB KINGZ) which treated chapter internal politics more like something from the Roman senate, with elements of the First Company suspected to have been sent to keep an eye on the Second because Sicarius may have been gunning for the position of chapter master.

Graham McNeill's books meanwhile show show the chapter in a very balanced light, proving why they are considered among the elite but never claiming they are without failings or totally above other chapters. In the case of that series, the final book set in Ultramar brings up the fact that it is a warrior society who hold any who do not pull their own weight with the greatest disdain. It's also build upon self-sacrifice, discipline and giving all in the name of Ultramar and the Imperium, not exactly the best elements usually found in utopia.

It also does bring up one great failing: The chapter's treatment of the Codex Astartes. The Codex itself is an exceptional piece of work, but Guilliman never intended it to completely replace all teachings or supplant all battlefield ingenuity. As the millennia went by, the Ultramarines suffered as they stopped treating it like Sun Tzu's Art of War and more like the gospel, to be held above all else and never ignored. While the series unfortunately does hammer down far too hard on the idea that Codex is a weakness and doesn't show it often enough as a strength, it brings up points to frequently support this and show why it was so effective. One story has suggested that it's not quite so much about how to be the ultimate soldier as a loyal astartes, which would make sense given the Imperium's attitudes towards creative thinking and how it leads to Chaos.

This was actually an idea which has long existed, only to be ignored in the last several editions. During the First Tyrannic War, the Ultramarines lost Prandium because the tactics they used were ill suited to fighting the Tyranids, inflicting heavy casualties among them and forcing them to retreat. After the conflict, Calgar was noted to enter several days of fasting and meditation in pertinence for this failing, for his arrogance, and awoke far later to begin re-writing parts of the Codex. This featured him contributing large sections on how to combat the Tyranids, resorting to strategies which went completely against the astartes' traditional blitzkrieg tactics.

The series eventually culminated in The Chapter's Due which was effectively one massive apology to Ultramarines fans over what Mat Ward had done, and tried to create a balanced perspective on all characters.

Sicarius was back to being an arrogant ace general and risk-taker, but one who had never truly faced failure and suffered from extreme arrogance.

Calgar meanwhile admitted that some Ultramarines victories (one in particular) were propaganda to help hide certain details from the citizens of the Imperium for their own safety. One example was the idea that Calgar had singled-handedly ripped M'Kar limb from limb during a prior invasion in 935.41M. The book, in fact, reveals that they had not been able to accomplish this at all and had merely imprisoned him within a Star Fort, sacrificing it and half a company of volunteers left to guard it, as it was sent spinning off into the Warp so it could never be found. This allowed the suggestion that some of the more ridiculous victories in that book truly were propaganda promoted for some reason, with even members of their own chapter believing it.

The actual book itself meanwhile showed the Ultramarines managing to fight their way out of the worst position possible. Honsou, a genius tactician of a Warsmith, had arrived with a force compatible to a Great Crusade expedition. With ten thousand traitors, astartes and xenos mercenaries at his back he stormed the system. He had full knowledge and understanding of the Codex's doctrines, had a way of bypassing Ultramar's orbital defences, and could have easily crushed the chapter thanks to sheer numbers. Worse still, he had M'Kar on his side who, unlike the one Ward wrote, was a geniune threat rather than a punching bag for whoever needed to be promoted that week.

The Invasion of Ultramar proved to be a harrowing experience for the Ultramarines, but along with elements of the Raven Guard, Mechanicus and Inquisition they managed to fight their way to victory. Using superior tactics, elements the enemy had not thought of and even a shard of an anathme buried millennia before, they emerged victorious. The enemy was routed, most of their leaders slain and driven out of Ultramar, and they succeeded in totally destroying M'Kar once and for all, but not without heavy casualties. Three and a half companies of the Ultramarines had been slain in the conflict, most of the Raven Guard along with them, and three of Ultramar's worlds would need to be completely re-colonised.

As I said previously, under good authors the chapter can be made interesting. Under a bad one like Ward (who has gone out of his way to try and retcon McNeill's books from existence), and those who buy into the prior codex's lore (Aaron Dembski-Bowden and Guy Haley unfortunately) they become an embarrassment. They can be written with flaws without compromising what made them great in the first place.

Docbutcher and [insert name with reply] dislikes this.

I was being overly simplistic with the reference to 1984 (though the setting, overall, is dystopian). There's a few statements by the human rank & file in Know No Fear about how the Ultramarines get upset if you're even 5 minutes late. "Everything should be as precise and considered as it were a military operation," or something to that extent. It's not quite 1984; it was my grasping for straws to find some amusing potential flaw or hubris in an apparently/overtly flawless 13th Legion.

You at least echo some of my commentaries of how they still illustrate some less-desirable traits despite how well they try to run things.

I am of the firm belief that there's no such thing as a perfect society or government (hence I like dystopian fiction so much).
Yes, in contrast, Ultramar appears immaculate, but that's all I ever gotten from Ultramarine players/authors/games/movies/documents/etc that I have encountered. There's never the slightest hint of a downside to them.
The only flaws that happen within the Ultramar system are because Xenos/Chaos is bad, and rarely/never because of the inherent frailties of man (something that is found within the rest of the Legions).

For another (less dystopian) counterpoint; let's consider Superman. Superman wants--with all his heart--to be human. He tries so hard to be human that he becomes a paragon of all that is good in humanity. However, he will never be human. Now this is what makes Superman compelling as a character. Nevertheless, you'll find plenty of comic/superhero geeks out there that dislike Superman because he's infallible and goody-two-shoes (e.g. "boring" to some people).
Ironically, an alien trying too hard to be human is a part of what's alienating about him.
[Now that's something I can enjoy! ]

You are absolutely correct; I am not as well read in all matters discretely Ultramarine. This is one reason why I am reading Know No Fear.
Regardless, I've read a fair bit of the Heresy series, and the Ultramarines do get mentioned & appear throughout.

However, Know No Fear would be the first predominantly Ultramarines book I've read. Thus far, it seems that the book just further reinforces my counter-point/explanation as to why there's such backlash against the Ultramarines.

*IMPORTANT NOTE*: It should be noted that I got into Warhammer 40k during the "Matt Ward" era (~5th Edition). Thus, all fluff and codices Space Marine I've encountered have painted the Ultramarines in the ways I've described thus far. In addition; my friend that got me into 40k is an Ultramarine fan of "Near-Wardian" proportions. ^_-
Please understand that it has been VERY DIFFICULT to find material that does not "tow-the-line" as it were. What you state at least gives me hope into enjoying the Legion at least a bit more.

Perhaps--given Dan Abnett's fairly clinical writing (works great for Sci-Fi)--that the already clinical/meticulous Ultramarines are coming across as overbearingly inerrant and goody-goody. I will sincerely take into consideration your novel references/recommendations for my next read.

I humbly invite any further recommendations of Ultramarine novels from you or anyone else in this community.

I also wish to thank how well-behaved and (surprisingly) helpful the people in this thread have been. I was expecting a lot of nerd-rage (I could be counted among those playfully jibing a Legion that people love ^_-).

honestly ive read the ultramarines omnibuses (out of mild interest int ehir chapter) and was so bored i am still rolling about in some great big mechanicus tank.

Do yourselves a favor and read the battle of the Fang it has Magnus the red...

SPESS TOMB KINGS ARE SOOOOOOOOO AWESOOOOOOME!

No sarcasm.

I compare an Ultramarine's personality to a Knight or Paladin, they have a VERY strict code of honor and sense of duty. Perfection is impossible even for a superhuman and that inner conflict is what allows for a great depth of character. People view Ultrmarines as arrogant, cocky, with OCD problems and honestly thru the novels this concept is reinforced. A sense of duty to a higher cause is not arrogance however, its devotion. I constantly hear "Ultramarines are boring because theyre not special". So a 9-10 foot tall supersoldier with two hearts who heals wounds like wolverine, spits acid and can chew through metal isnt enough for you? You can bairly even call a Space Marine human. They have a interlocked superstrong ribcage that acts like a bullet proof vest, skin that changes black so they can resist high levels of radiation and glands that give them the ability to injest deadly poisons like it was the can of soda in your hand! As for theyre color scheme, its not suppose to be militarisitic. How many camo schemed marines do you see in the 40k universe? Maybe the ones people custom paint... They dont need to hide, theyre badass supersoldiers with 10,000 + years of tactical knowledge and practice. A spartan from the movie 300 would be a housewife in comparison. When it all comes down to it however, the real significant identifier of an Ultramarine is the Roman sterotype, which honestly is a great basis for a proud sucessful chapter.

*sniffles* But I LOVE Magnus! ;_;

[He really screwed up so royally in the end--poor guy].

But then I also love Space Wolves, so I shoudn't be entirely be disappointed with Battle of the Fang.