You can download the soundtrack for Tomb Raider: Underworld for free at TombRaiderChronicles.com. The download is 198Mb for the complete package. You can also download the sountrack for each chapter individualy.
A demo of Tomb Raider Underworld is now available for download on Xbox 360. I made a YouTube video with around 7 minute of gameplay. I think the graphics are good, the gameplay too. So this will be a definitive buy when it comes out in November.
The screenshots bellow is from taken from the video I recorded of my gameplay.