I loved the movie, and I especially loved Will Smith in it. It wasn't at all what I expected, and for that I love it. The last 20-30 minutes were somewhat disappointing, especially the ending, but as others have said, there's not much else really that they could have done without taking away from the rest of the movie.
New York was amazing. There were a number of subtleties that I briefly glimpsed and couldn't quite grasp. I loved the ragged posters "God still loves us, but do we love God" or something like that. And did anyone else notice the billboard with the batman logo superimposed over a superman logo? There's the butterfly of course which, while I love to see symbolism drawn out like this, its implications kind of bothered me, that all the happenings were simply matters of fate, that Neville was pre-destined to do these things which I didn't feel matched the story, and which certainly took away from Neville's overall character.
I do agree that the cg was bad, well not bad, but unrealistic, well not unrealistic but it just wasn't done well enough to match the super-realistic surroundings. The lions at the beginning of the movie in particular kinda bothered me. But CG animals always do really. The 'zombies' were actually quite well done at some points, namely in the dark, in the scenes where Neville follows Sam into the warehouse. The faces, especially that of the head zombie, were unrealistic of course, but I've yet to see convincing CG faces from any source. No matter how well done CG is, we still know it's CG, and therefore we're looking at nothing at all essentially(as compared to puppetry and makeup, which while often unrealistic, has a physical presence that doesn't offend as much as CG can.)
The story really was fantastic, it almost had the feel of an indie film, but with all the money of a truly Hollywood film. I think the only reason a person wouldn't be able to appreciate it is if they've been spoiled by Hollywood, in which case the movie's bound to be a disappointment, but that's not a fault in the film. The film's not for an impatient immature audience. Unfortunately, I think the way the trailers were edited allows too easily for misinterpretation, and that's why there are so many disappointed people.