One thing I would've changed...
This is just my opinion, but in the scene near the beginning when they're driving to the cabin and the hawk crashes into the energy grid and dies, I think they gave away too much.
If the hawk had just suddenly caught fire and fell that would've been fine and it wouldn't have exposed so soon that there was a sci-fi slant to what they were going through as opposed to evil demon stuff.
Yes, the movie started with the scientists, so you knew they were somehow involved, but that scene with the hawk just put too fine a point on what was going on.