This is one-half of a pretty decent movie, unfortunately it's also one-half of a really awful one.
The good half occupies most of the first and second act, with Will Smith doing the last man on Earth thing in a slowly deteriorating, deserted Manhattan in what's at least a tonally-faithful reworking of Richard Matheson's seminal scifi novel. A supposed cure for cancer has instead wiped out the human race, and aside from Smith's Robert Neville anyone who survived is now a shrieking, light-phobic mutant/vampire. Good start.
Sadly, the film doesn't have the stones to follow Matheson's work through to it's grim, pitch-black final twist. So instead we get one of the most awful third-acts to a good movie since I don't remember when; as what started out as a damn well-mounted work of apocalyptic scifi with a grand and insightful turn of man-going-crazy acting from Smith get's tossed out the window in favor of thuddingly moronic religious tripe and a bunch of nonsense about butterfly-symbolism; not helped by some of the worst looking CGI creatures you'll see this year. A total disappointment.
FINAL RATING: 4/10