Shaun White Snowboarding is built on the Assassin's Creed engine, and Ubisoft Montreal has promised that physics will supercede animation. They also promise player stats and supported leaderboards, as well as Dolby 5.1 Surround Sound. Sadly, the game resolution is limited to 720p, and future DLC has not been confirmed.
Exactly how 16 friends will join up has not been specified...I think it's safe to assume that drop-in/drop-out gameplay will be available, at least for free-run play in the open world areas. Either way, Xbox 360 users will get the full benefit of this game, thanks to the New Xbox Experience coming November 19th, just three days after the game ships.
If you get tired of racing and pulling stunts, the game will feature on-foot movement for hiking and exploring, and players will be able to engage in snowball fights. To top it all off, you can make in-game films of everything happening, and upload them for others to view. Whether this means actual in-game camera control and capture or a replay system, it's still a welcome distraction.
All in all, this game is an exciting prospect for co-op gamers, especially the casual sort. Odds are that if you like playing 8-player Burnout Paradise, you'll have fun with Shaun White Snowboarding.
UPDATE: We do have some info on the Wii version, which looks to stand on its own as a solid splitscreen co-op title... Read DjinniMan's previous post here.