Sega's posted the Sonic Unleashed demo on Live, as Nelson reports. Blurb:
[ESRB: E10+ (Everyone 10+) ANIMATED BLOOD,FANTASY VIOLENCE] Sonic’s on a worldwide adventure as speed is re-imagined! Powered by the Hedgehog Engine, Sonic Unleashed merges classic Sonic gameplay with next-gen innovation. Explore the first location of this all-new adventure in the Sonic Unleashed Demo, reaching speeds that you’ve never seen before!
Try it. You may like it.