I make mine now, but I used to buy the packaged binding. I like that when I make my own I can make bindings from prints and make sure the colors really match, and also it's cheaper. Plus, when I used the packaged stuff, I usually had a spot or two on the back that didn't get caught by the stitches, and I'd have to go back and fix it.
I usually cut my strips 2" and fold in half. I like a very narrow binding.