I was pretty surprised to see that Will Smith could actually manage to play a serious role - but except for a few annoying bits (especially when he was talking to the mannequins) - he did very well playing the last man on earth.
After a cure for cancer turned out to be a virus instead, most of the human population - as well as a lot of animals - are either dead or has mutated into bloodsucking dark-seekers. The dark-seekers are really cool. I've never liked fast moving zombies (it kinda breaks the George A. Romero "zombie logic") - but since they are in fact not zombies but mutants - I accepted it, and just enjoyed their cool movements and aggressive attacks. The action scenes are completely unrealistic at times but since it is an action movie I just accepted that as well.
The special effects are amazing, and it is very cool to see all the familiar buildings and places in New York. Places that would normally be full of thousands of people are now being completely abandoned. A few shy animals are all you see. The fact that there is almost no music and mostly just the total quietness of an empty New York is really cool and adds a lot to the atmosphere of the movie.
The religious and moral bullshit near the end I could have done happily without, but for the most parts I enjoyed the movie and found it pretty cool.