Watched it again recently, two issues (spoilers)
I enjoyed this movie although it wasn't as good as the thoroughly excellent District 9.
Two things struck me watching it again (SPOILERS):
1) The scene where Max gets irradiated was really badly written. Don't get me wrong, workers at factories have been getting themselves killed by industrial machinery in all sorts of ways for centuries, but the way it happens is totally at odds with his character. The scene is supposed to show how worthless human life on Earth is, but even a uncaring manager wouldn't want to have to replace a broken machine.
Max is shown later to be highly intelligent, being adaptable and being able to make smart tactical and strategic decisions. That is completely incompatible with someone going into this room when he knows the equipment is on. He could have blocked the outside door, he could have shut off the machine, he could have asked the manager or a coworker to observe, but he did none of those things.
2) The ending. The Earth is overpopulated and polluted. Now people on Earth will get perfect healthcare and no longer age? Wouldn't that make the first two problems much, much worse?