Edited to add: No significant spoilers in this entry itelf, but there are big spoilers in the comments.
I got the very strong impression at the time this movie came out that it wasn't very good.
But I like Will Smith, and I like action movies, and I figured it might be kind of fun, in a mindless Hollywood action-adventure kind of way. So eventually the movie turned up on my Netflix queue, and after it sat on top of my TV for a couple weeks, Kam and I watched it.
And I liked it. Quite a bit, certainly a whole lot more than I expected to. And it's a whole lot smarter (and funnier) than I expected.
I think that what happened is that anyone who knew anything about Asimov's work refused to listen to warnings that the movie had little or nothing to do with Asimov's work. They went into it expecting a movie of Asimov's work, and they were sorely disappointed, because (let me repeat it) this movie has almost nothing to do with Asimov's work. And so pretty much all the reviews I saw from the sf world said "This is a stupid travesty of a movie because it's nothing like Asimov's writing."
To be fair, the filmmakers invited that kind of criticism, by using Asimov's title (which, btw, was originally borrowed by Asimov's publisher from an old story by Eando Binder that had been one of Asimov's original inspirations), and the Three Laws, and the names "US Robotics" and "Dr. Susan Calvin" and "Alfred Lanning." (Plus a couple of specific plot elements from a couple of Asimov's works.) It might be reasonable to expect that the movie would use Asimov's plots. --I say "plots" instead of "plot" because most of the sf reviewers I've seen talk about the book as if it were a novel. It wasn't; it was a collection of nine short stories, written over a period of 35+ years, each with its own plot.
But the movie does not, in fact, use the plots of the stories in Asimov's collection. So my advice to anyone considering seeing this movie is: forget anything you might know about Asimov's work. Pretend this is an entirely new movie with no sfnal antecedents. If you like action-adventure movies, and you like science fiction done well in movie form, and you can get over the lack of Asimov stuff, you may enjoy this movie a lot.
The closing credits say that the movie was "Suggested by Isaac Asimov's book." That seems to me an accurate description of the relation between the two. (I'm baffled by Roger Ebert's claim that it was wrong for characters in the movie to say that a character in the movie created the Three Laws. Ebert says everyone knows it was really Asimov who came up with them; I'm not sure why he thinks that's remotely relevant, since obviously in the world of the movie it would be a character in the movie who came up with them. Presumably even in the world of Asimov's books, it was a fictional character who came up with them, not Asimov himself.)
So I'm now going to leave the Asimov stuff behind, in favor of talking about the movie itself.
One of the many things I liked about it was that the world of the movie felt solid to me. As with several other recent sf movies, it seems to me that the filmmakers gave some thought to what their future world would be like; they gave it enough texture that it didn't feel like just a thin veneer of sf on top of an otherwise modern-day setting. (The opening scene does feel like a modern-day setting, but there turns out to be a good reason for that: that scene is set in the apartment of Will Smith's character, a detective named Spooner, who hates robots.)
Another thing I liked about it was that it kept surprising me, all the way through--even the very final scene. Maybe this merely indicates that I'm naive about movie structure; others may have found it more predictable. But there were at least half a dozen key points where I was sure I knew what would happen next, and not only was my guess wrong, what actually happened was much better and more interesting.
Perhaps the biggest thing that I liked was that it was not the movie I assumed it would be from the preview. I figured that Spooner was going to spend the whole movie warning people about the dangers of robots, and then at the end, everyone would find out he was right, that robots are evil and technology is bad and must be stopped. And for the first half-hour or so, it sort of looks like that's the movie it's going to be--but it's absolutely not. That's neither the plot nor the theme of the movie.
Another thing I liked was that there are a lot more black people in the future as portrayed in this movie than in most Hollywood movies. (The Matrix and Strange Days notwithstanding.) Three major black characters, all sympathetic and well-portrayed, and a fair number of others in background roles. (Okay, so it's a little surprising that only thirty years from now, Chicago appears to have gotten over all prejudices having to do with skin color; but I can forgive that, and there's a cute line that does momentarily foreground the issue.)
I wanted to call attention to one of those major black characters in particular: I loved Adrian Ricard as Spooner's grandmother. And speaking of actors, though not black ones, I was also delighted to discover that James Cromwell (one of my favorite actors) has an important role (although not a lot of screen time). And I just figured out why a prominent robot in the movie had a familiar voice: it's Alan Tudyk, best known in my circles for playing Wash in Firefly and Serenity.
I rolled my eyes a little to see that they still have product placement in the future--in the first five minutes, there are two very very prominent product placements that are basically irrelevant to the movie. But again, I can forgive this; not a big deal. And it's one of the few things I rolled my eyes at.
It should also be noted that the movie relies fairly heavily on standard action-movie genre conventions--to pick a minor and fairly unspoilery example, this movie is yet another good example of Rob S's idea that an action hero's primary D&D characteristic is Constitution, as Spooner takes a lot of damage in this movie. If you get annoyed at the standard kinds of things that happen in action movies, maybe you should skip this movie. But it doesn't rely on them nearly as much as most action movies do (and it even has unusually good in-movie justifications for a couple of them), and anyway those kinds of genre conventions don't really bother me.
Back before the movie came out, there was some discussion (in my journal as well as elsewhere) of whether the Three Laws had anything to do with the movie. I think it's not too much of a spoiler to say that, even though this movie has almost nothing to do with Asimov's work per se, the Three Laws are indeed central to the plot and to the world of the story. I can more or less imagine the story working without explicitly referring to the Three Laws, but I suspect something similar to them must have been part of the story from the very beginning. Here's what the IMDB trivia page says about the development of the script, btw:
The movie originally started as a screenplay entitled "Hardwired", a classical-style murder mystery that read like a stage play, and was very much in the spirit of Asimov's "three laws" mysteries.
(According to that page, various people who worked on the script later made it more in keeping with the blockbuster action genre, and then fiddled with it to incorporate bits of Asimov, and then tailored it specifically to Will Smith.)
In summary, I think this is a good science fiction action movie, with sharp dialogue, compelling characters and situations, and good special effects. If you can avoid getting too hung up on the Asimov thing or the action-movie genre conventions, I definitely recommend seeing it.
And btw, I'm now retroactively disappointed that this movie didn't make last year's Hugo ballot (in the Dramatic Presentation Long Form category, of course). I liked this movie significantly better than anything else in that ballot category that year except for The Incredibles. Since Incredibles ended up winning, I can't complain about the result, but if I could retroactively replace any of the others on that ballot with I, Robot, I'd be happy to do so.