PS3 demo did nothing for me. SSX3 level game play and sound track are the things I was interested in, not improved graphics. The demo failed to deliver on either. I will have too see if any of the kiosks in my area have game rentals, because no way would I buy it at this point.
What music there is, is terrible (for my taste), and wiping out seems to be much more difficult to do. I realize you can purchase better gear and improve skills, but it will have to greatly enhance the experience over the demo to get me to buy it at anything over $20.