I didn't know what to expect going in, but opening in a desert scene with a bunch of commandos with guns made it really hard for me to switch to sci-fi mode once I realized what kind of movie it was. that might say more about me and my expectations than the actual film, tho.

other than that, I thought the dialogue wasn't particularly well written, the action scenes were OK but nothing special, and the girl who played Nile just... wasn't very good, to the point that it became distracting.

in regards to your point about the humor, while I agree that a little wouldn't hurt, I do actually buy that these characters would more likely be feeling the weight of their immortality as a curse, (particularly Charlize's character), so the mostly dour tone worked for me.