First of all, this film wouldn't have worked if it hadn't been set in South Africa. Ignoring the apartheid mirroring (the film is based on the writer/director's direct experiences of it), the humour based around the naivety of the main character at the start is fundamentally South African and lacks the seriousness that a US lead would have injected, and the scepticism that a British lead would have, to the film's advantage.
The lack of sympathy I felt for Wikus throughout a lot of the movie is pure genius in my opinion. He comes across as being completely influenced by the regime he's employed under and has chosen to disregard his own feelings towards the alien 'invasion'. As the viewer we're constantly torn between his selfish ambition to escape the situation he's found himself in and his empathy to helping the Prawns. At least three or four times I felt sorry for the man, only seconds later to hold contempt for his actions. I particularly liked the idea that he could only truly feel for their plight by becoming one of them.
The acting felt more naturalistic than most films I've seen - practically genuine pain/panic responses and a lot of talking heads/documentary style interviews with the public that might as well have been set up as if they were talking about a real event. If the subject matter hadn't been aliens, for the most part it could have passed as a real documentary. There was also a clever extra layer caused by the idea that as they carried out their eviction duties they were being filmed, so the characters had to behave on camera, and react to it.
Finally, I was amazed at the fluidity and blending of the special effects. I'm told that most of the effects were added post-production and if that's the case I've no idea how they filmed it. Considering the relatively modest budget of the project, the realism of the scenes where Prawns interacted with humans, and the grimy feel of the alien technology was better than any I've seen in a big budget film. It felt seamless. The final scenes were incredibly kick-ass, and at no point did I stop to think 'how did they do that?' - I just took it at face value until I stopped to think about it afterwards.
I'm struggling to think of a reason not to give this 10/10.