Addressing some of the complaints I have seen around other message boards and the net:
One thing that I've seen all over the internet is people saying that they really want a sequel. I strongly disagree. I think that a sequel would undermine what was made to be intentionally ambiguous about this film. I like that the ending is left open to interpretation, and I really feel that it should be left that way. The plot of a sequel would almost have to be entirely action oriented, and while the action was a large part of this film, it was not what drove the plot. I also think that the last scene would be made far less emotionally powerful (for me at least) if a sequel was made.
Another thing I have seen people complaining about is what they see as plot holes. They want an explanation of how the fluid turned Vikas into a prawn, and think that since the audience is left without one, it becomes a plot hole. Once again, I see it as better off left unexplained. We dont need to know how he turned into an alien, that has no bearing on the plot, what matters is that he is turning into one, not how it happens.
Overall though this was one of the best films I've seen in years, and definitely my favorite since The Dark Knight. I look forward to more work from Blomkamp in the future.