Just finished up I Am Legend. I dug it.
Even though they basically just took elements from the original story, they used them well to make a good story.
The infected were pretty well done. I liked the way they were semi-reimagined as vampire/zombies as opposed to your run-of-the-mill vampire in the novel.
I didn't have any problems with the CG (some of it looked CG, but I thought it was forgivable), but I did see on my tv, rather than a theater screen.
The only thing that bugged me was whole Fred/trap thing. It did seem that the infected set the entire thing up, IMO. Despite the shock of seeing Fred it would have been pretty stupid of Robert to walk right into his own trap. Besides, where Fred was placed was too convenient for the trap. I wish that had been explained somehow.