I've been video taping deer for years, first vhs, then 8mm, then hi 8, now digital. I think digital has a lot going for it. The quality is good. They make really compact recorders now so they are easy to include in a backpack.
I agree that an extra battery is very important. Also carry extra tapes. I hate to be getting something really good then see either the 'end of tape' or 'low battery' signal flashing.
A couple other things to watch for are good image stabilization to minimize image movement on hand held shots and a good optical zoom. The digital zoom just enlarges the pixels so a lot of ditital zoom doesn't do you much good. Optical zoom is how close the lenses bring in the subject. I like at least 20 optical.
There are lots of good cameras out there and the prices keep coming down. You need to just look around. I'd about rather forget to take my bow than to forget my video camera.