Just got back from District 9 - it was about a hundred different kinds of amazing. It might just be the high of seeing it for the first time, but I'll go out on a limb and say that it's easily the best action sci-fi film I've ever seen - yes, it's better than Aliens. And the CG never once stood out to me as being CG, which is extraordinarily rare these days.
I highly recommend it to everyone here. Amazing.