The Hurt Locker beat Avatar at most of the big award ceremonies so it's no surprise at all it won (it was the favourite to win I believe - just Avatar is a more famous movie, so more was heard about it)
I had guessed a split - Bigelow for Director, Avatar for Picture. I wouldn't have given Avatar a chance, except that they opened it up to ten nominees this year - meaning the "art house" voters had their votes diluted, if you will, between more pictures. At least I was half-right.
We have an Oscar pool with about six of us here. I've won three years in a row - this time by a single win (I got 15 right).