What a coincidence, I just watched this today. Thought it was near-legend 2/3 of the way through, but when...
**Spoiler! But you shouldn't be reading a thread about a film if you haven't seen it anyway...**
The sunburned-zombie killing machine showed up, the film became what it had mocked just an hour before ("if we split up, the aliens will kill us one by one"). I had just wanted a bit more character development up until that point, but when that happened, things went pretty sideways. It just didn't make sense based on the narrative that had been presented. Much like Event Horizon (only done better here), it was a great premise that gave way to convention. Still...visually, thematically, and (especially) sonically (Underworld are great), it was fantastic. I'm a picky bastard and this nearly did it for me. A bit more deliberate pacing in the beginning, and a bit more "real" threat at the climax and it would have been poi-fect.