Having now seen the movie, I have mixed feelings. If you take the movie divorced from the comic, it's great. Really a great measure of fun for the teenage to early adult male all around. Having said that, I understand why people have been saying this ending doesn't work as well... because it doesn't.
Here are my thoughts on the ending right now... and mind you I worked 8-8:30 today, changed out of my scrubs, went for dinner with friends, and went straight to the movie... by multiplying the threat outside of NYC to not only LA, but to major cities in all world powers across the globe, you necessarily back yourself into a corner. Any world peace that comes about would be short-lived, since people are inevitably going to swing back around and point the finger at America. "The superman exists, and he is American." That's an iconic line, and not one which I am sure anyone is prepared to forget. Yes, in the short term, everyone on the planet may be ^^^^ting their pants out of pure fear and awe of this power that simultaneously murdered millions of people in a calculated attack spanning the globe. That said, now what? We hear at the conclusion of the film that American and the USSR have agreed to unite against this foe, an act that circumvents nuclear war. However, it's not really laid out as to how they plan on going about this, and if there could be any practical plan at all to deal with Dr. M. Granted, it's never made explicit in the graphic novel how humanity's leaders plan on dealing with interdimensional squid either; even then, I think it's the confusion and hysterics. If you have two piranha in a tank, and they circle, prepared to fight one another... now you throw in a juvenile bull shark, and those piranha are huddled side by side against their common foe, not really sure what to do about it, but unifying to present a strong front, however futile.
That's what the ending in the book calls to mind... but when the dust settles in the movie, the buck returns to America, and to its leaders, namely Richard Nixon who called Dr. M to Vietnam, winning the war in a week's time. There's always going to be a wary eye cast towards America, and I do think the movie did its best to emulate the omnipresent fear of a looming, powerful threat in Dr.M, but fell short. Reason being that once he removes himself from involvement with humanity, years down the line people are always going to remember that the being who perpetrated a mass killing of unparalleled proportions was an American, and they're going to want to bring someone to book... or at least will always be a tad bit more incredulous about Americans. It's a peace that ultimately, I think, dissolves in a much shorter span of time than the other alternative, being that the only city attacked was on American soil in the book, and the culprit does not have ties to the US, but another dimension entirely (so people think). It does achieve the same result as world peace, though not in a manner that seems as airtight and lasting as that in the GN. Close, but not close enough in my mind.
What I liked... well, I LOVED the movie as a whole, again when it's taken separately from the source material and viewed as a narrative unto itself. I like to consider movies that way, be they LotR, HP, JP, JAWS, etc. The movies are always good, even magnificent, but need to be taken separately from the books in order to be appreciated in their medium. That's the case here, for me at least. What I was totally immersed in was JDM as the Comedian. Nailed the part. Nailed it to the ^^^^ing wall. Dead on. Perfect. Quite literally flawless. I know everyone keeps singing the praises of JEH and BC, but JDM was the actor who just seemed as if my imagined vision of the Comedian came to tangible reality.
JEH was also magnificent as Rorschach, though it took me a good while to get used to the growl; I always imagined a more subdued, gruff monotone as opposed to a forceful growl. Other than that he was also perfect.
Billy Cudrup was, like the aforementioned actors, wonderful as Dr.M, and brought an almost doleful air to the character who I personally thought of as being more booming, detached, but booming and powerful; and I have to say, I like rather mournful indifference better, and it offers up a new perspective on the character for me.
Ozymandias differed really only in terms of brawny physicality, other than that he too was an exact replica of his comic character. I'm so very pleased with the casting in this film.
And while they didn't stand out as much for me personally namely because I don't think they were as over-the-top in the story to begin with when placed alongside the other characters, Malin Akerman Patrick Wilson, and Carla Gugino, as Laurie, Dan, and Sally respectively, were also well-suited to the parts. I thought maybe Laurie could have been more of a ^^^^^, Dan was the perfect insecure science geek, and Sally... well, Sally as basically alcoholic longing to recapture her youthful image was interesting, but the Sally of the GN seemed to have a yearning within her, though living with a sadness checked by her joy of life. All together, great cast.
What I didn't like, aside from what I've already mentioned, was the abbreviated and altered explanation of how Kovacs became Rorschach, and Rorschach's meeting (singular) with Dr. Long. It seemed to change the character in changing those components... but maybe that's just me. I thought those were the most emotionally powerful moments of GN, and that they were watered down for time constraints, and ironically to amp up the gore (I'm thinking of the meat cleaver in place of the fire... which really didn't do it for me as I imagine Rorschach really wanted that man to suffer for what he did, and an instantaneous death like that seems inappropriate for the scene). And the one memorable moment when I literally laughed aloud for some time upon first reading the book, the scene when Rorschach assails Moloch from inside Moloch's refrigerator, was cut entirely... and melded with the second time Rorschach surprised Moloch in the kitchen, leaving the note in the refrigerator.
Those were my two big gripes with the way Rorschach was handled. A few minor things, such as Dr. M always carrying the photo of he and Janey with him, rather than going back to the billboard in the Bestiary at Gila Flats to retrieve it. A minor gripe, but something I thought was touching and intriguing in the GN. More significant, and I think done for shock value and gore in the movie, was the fact that Dan and Laurie killed... and killed several people, rather violently at that. When assailed by the gang in the alley, one man is stabbed in the neck with his own knife, another has his head completely twisted about on his neck like a wind-up toy... scenes like that make you actually understand why the Keene Act should have been pushed through. Hell, it made the Comedian's "crowd control" look docile.
Those are some of my tentative thoughts. I'd like to see it again to get a better sense of some things and to search for smaller details, but it's been a long day, and a late night, so this is the what I have tumbling through my head right now.