I finally watched I AM LEGEND last night, and as you saw from the title of this post, I was a little disappointed.
I read the Richard Matheson book several years ago and really enjoyed it (it IS a classic). So naturally, the ending didn't live up to expectations. I won't spoil it here, but it seems like it would be a good idea to leave the book's ending since it EXPLAINS the title of the film. Everybody asks me why the movie was called I AM LEGEND - and all I can say is, "read the book." It seems like, once again, the studio pushed for the "happy Hollywood ending"- essentially making this film just another run-of-the-mill zombie movie. I encourage everyone to read the Matheson novel - it is much more satisfying.
My other major problem with the film is the CGI zombies. The zombie/vampire/monsters in the film are entirely done in CGI. Too much CGI is always a bad thing for the simple reason that you can't quite make CGI characters look 100% convincing. Gollum from LOTR is the best I've seen with a CGI character, and nobody else has come close. I believe the "scare" factor of this film would have greatly benefited from real actors in makeup - I'm glad GDT shares this philosophy.
I am pleased however that a studio took a chance on a big budget special effects horror movie, though. This film did pretty good at the box office, so I'm hoping that movies like this will open the doors for ATMOM to get made. GDT is insisting on keeping out any "happy Hollywood" ending in ATMOM and - judging from LEGEND - seems to be a just battle.