You're absolutely right. It was an amazing film.
Some of my friends don't like it because of the lack of a sympathetic main character, but I found Wikus' bald-faced self-interest a refreshing and realistic departure from the normal squeaky-clean, or nasty-but-sees-error-of-ways-and-redeems-self hero.
Wikus is closer to the second one, but he never turns around and makes a moral stand based on what's right... he basically does what he can to get himself out of the situation, learning a few lessons along the way at a very late stage. He never quite gets to the squeaky clean phase, even when his anger compels him to risk his life to ensure Christopher's success.
There are some minor logical conundrums to the plot, but nothing big enough to disrupt the suspension of disbelief. At the end of the day, the story, fantastic acting, unique - and in Hollywood terms - exotic setting, and incredibly expressive effects make it a pleasure to watch.