I knew nothing about this going in, except for having seen one 2 minute preview. Spaceship stalls over South Africa. I didn't even know that the aliens were brought down to Earth and living in an internment camp (called District 9, which is where it got the name.)
The advertisements have been all over LA for about 3 months, and it has been just about the most annoying ad campaign I've seen yet. Bus stops were all marked with "this bus bench for humans only. report all non-humans to authorities immediately." type slogans. I was almost prepared to hold the ads against the movie. But it was too good.
The guy who plays the lead, Sharlto Copley was amazing. Christian Bale, Daniel Day Lewis, or any other actor of the calibre could not have done a better job. And in fact, I think had they been in the role there would already be Oscar talk for it.
There are some things I would have changed (mainly about how they tried to tell the "prawns'" side of the story) but it is so entertaining and so well filmed that I didn't mind the things that i would have changed. And the special effects hold up. You don't even think about them until after you leave the theater. I don't like watching special effects movies where you're thinking, "wow that looks fantastic." while you're watching it. Because if you're thinking that, obviously the movie isn't capturing your attention. If you're thinking, "that looks horrible." A) it looks horrible and b) the movie isn't capturing your attention.
anyway, solid. go see it.