The movie is considerably better than I'd expected it to be. I'm going to leave it at that to avoid any possible spoilers. Maybe I'll write a spoiler entry later. But if you enjoy sf-action movies, "I, Robot" is well worth seeing.
On a related note: it's hard for me to say if Will Smith is a good actor or not, because in all the movies I've seen with him, he's always playing the same character. Different backgrounds, different settings, same action-hero smartaleck. However, I can say one thing for sure: he's a fine performer. A lot of fun to watch. He may always be playing the same character, but that character always feels like a real person. He's very much the star of this film, and he carries it well.