We surrounded a two acre garden with 8' black polypropylene deer netting last spring, and it has kept out deer, dogs, moose, etc. I wouldn't bother with less than 8'. I was a good girl, followed instructions, and tied white ribbon to hang and flap from the fence every 10' at chest height. The deer see this and don't run into the fence. I have watched deer walk along an entire 350' side of my garden, looking in, but not even trying to jump. The fence ended up being a little loose on top, which makes it flop over the deer's head some. They can't see the black netting very well, and so are not able to percieve the height and therefore are unwilling to jump it. It has worked beautifully for me and held up very well over the winter with several feet of snow. It is also very important to use soil staples as directed to hold the fence snug to the ground. Otherwise the deer will scoot under. Luckily my cat figured out how to get in and so I still have mouse, vole and gopher patrol.
I have used electric fences in the past, and much prefer this for ease of installation, looks (the black netting is hardly visible, especially when installed tree to tree), and ease of maintenance (none so far). It also doesn't scare the **** out of you if you touch it.
Of course, deer are different from area to area. But I do recommend this fencing highly. The leftovers also come in handy for all sorts of things. We are now using it in place of chicken wire on chicken runs and chicken tractors. No more bleeding hands!