First of all, if you're an Asimov fan, you're probably aware that the script of "I, Robot" is only tangentially based on Asimov's robot novels and stories. The screenwriters, though, make no attempt to disguise that, claiming the script was "Suggested by Isaac Asimov." If you are not an Asimov fan, I should warn you that, for example, his "starter" robot book, "The Caves of Steel," is so totally different from this movie, it's like they're not even from the same universe.
My work schedule is such that I can only see movies during the summer, but each summer I see dozens and dozens. Last summer, for example, I saw practically everything playing at the theaters within the space of a few days. "I, Robot" was the film I liked the most. I vowed I would get the DVD as soon as it became available.
What I liked most about this movie was the script. It was by turns funny, suspenseful, thought-provoking, etc. In fact, it's a really good script to study if you're into writing your own: it can boast textbook models of how a writer should handle reversals, foreshadowing, payoff, character arc, etc. And the conclusion and the prelude both made sense, total sense! In short, not a line out of place.
Other things that could sink the movie are held in check: Will Smith, while perhaps not the ideal candidate for the job, delivers a believable and versatile performance.
The special effects shots help the movie along, rather than drag it in their wake. What noticeable shots there are really do more to creep you out than overawe you (e.g., the horde of evil robots scaling the USR building).
I was very surprised to read many reviews of this movie (after I saw it), which panned it. It is very difficult for me to see how somebody could see this as a stinker, and I'm the kind of guy who usually only likes about 1 out of every 20 movies I see.
Naturally, there's zero depth to the film, of course; as long as you know this beforehand, you'll be unlikely to regret investing a couple of hours in this movie.