1) Internet connectivity. Without it I'm mostly dead in the water.
2) Screen resolution. I want as much code/information on the screen as possible. I currently have a 1920x1200 Dell myself, and am I bit scared/saddened that I won't be able to replace it.
3) Memory. Always good.
After that come processor speed and storage space. I suspect my next machine will have SSD, because I've heard that it's such a dramatic improvement.
I completely agree with Linus though - I very much want a high resolution laptop screen.