I agree with IADroptine, the cold can drain your battery. I just bought a Sony digital camera and have filmed several smaller bucks, and the recovery of the buck I killed in Iowa on Nov 2. Also, the comment on manual focus is right on the money. I have some tree limbs in focus, with out of focus deer in the background.
To try to keep the camera warm, I tuck it inside my down vest which I wear under my camo coat. Between the body heat and down, it has helped some. One more little hint, take an extra tape along.
The video camera has added a whole new aspect to my bow season. Every time I come home, my wife and kids ask "what did you see?" and we watch it on TV. When they get a little older, hopefully I'm building an interest in my daughters so they will want to tag along with dad.
Happy hunting (and filming) MO