The demo weighs in about 720MB and gives you a chance to check out the single and multi-player. Here are a couple of mirrors were you can download it:
4Players Action Trip FileShack Gamershell WorthPlaying .torrent file
Note: ATI graphics card owners must install this hotfix first. This hotfix will be part of the next Catalyst driver.
The final game is expected on September 28, 2007.