Having seen District 9, I can attest that this one truly does live up to the hype, which means if you're looking for a playfully allegorical movie about oppressed aliens in South Africa that both mirrors apartheid and delivers the sci-fi/action goods, this one's for you. Here's my review for Moving Pictures.
But I'd like to take up a small amount of this space to point out that the alternate reality game (ARG) designed to build buzz for the movie over the last several months is almost as interesting as its actual plot. Take a look at this Wiki page outlining the complex network of websites set up to reflect various facets of the District 9 universe. This sly online marketing technique has been employed at least since Blair Witch (although you can find traces of it in earlier instances), and The Matrix movies took it to an extreme that alienated casual viewers, but the approach has nevertheless gradually developed into an art form in its own right. Last year, The Dark Knight had a fascinating cross-media promotional scheme that stretched its plot across various media; District 9 seems to have followed in Batman's footsteps. I am still waiting to see this kind of transmedia experience applied to a non-genre movie, something with plenty of drama but closer to real life. Documentaries have done this quite well, but a naturalistic work of fiction (such as The Hurt Locker) stands to benefit tremendously from such an approach.
It's not an impossible task, but somebody will have to actually care about the process of extending the story to these outer limits. As Scott Kirsner recently pointed out, audiences responsive to web content don't like insincere promotional campaigns.
Needless to say, District 9, a reasonably low budget movie with a built-in genre-loving audience, has nothing to worry about.