(at around 14 mins) The creaky first step in Dr. Maggie Dalton's house does not creak when she and Frank Turner walk downstairs together.
The amount of rainfall during the climax changes between shots; it's heavy when it's seemingly CGI, and it seems light whenever Maggie is alone in the shot.
Several times, night vision cameras are used to reveal the invisible characters. This should not work as night vision technology just enhances ambient light to make objects easier to see in low light conditions. It is not like Infra-red heat detecting technology as used in the first Hollow Man (2000). This technology is more complex and too expensive to be included in your average camcorder.
(at around 48 mins) At the gas station in Seattle a man asks if the ferry to Edmonds runs at night. Edmonds is on the Seattle side of the sound.
When Maggie was talking about the previous project supposedly from Hollow Man (2000), she said 5 people worked on it, when in the movie there were 7.