I take lots of pictures, but not one of each gift opened. I know I'd never scrap them all. I take a picture of them opening their 'big' gift and ones from relatives that live far away. Otherwise, it's kind of hit and miss what I take pictures of. My kids don't mind. In fact, my daughter (10) tells me that it is one of her favorite parts. She loves looking back at pictures from when she was little and seeing what she got.
My kids are really slow to unwrap stuff though. They find a gift, unwrap it, open it, play with it, and then set it aside before moving on to the next. Unwrapping gifts takes all morning (which is just how I like it) because the kids stop to play with everything as they go along.