Just seen it- I have a few minor niggles with plot holes and unanswered questions, but overall, I really enjoyed it.
It's shot a bit differently to most hollywood films. It starts almost like a documentary, and I thought it was going to be another cloverfield (which I didn't like), but it picks up after the first 20 minutes or so.
The effects are good as well, though pretty gruesome in parts, and as someone else said, it almost seems like a very subtle black comedy in parts, though not sure if that is intentional or not?
Either way, I'd recommend it.