The new ATI R600 graphics card has a leg up on the Nvidia G8x: a built-in sound card that can send audio directly out over a HDCP/HDMI link. The Nvidia, due to a lack of onboard sound, can't do full HD surround sound on Vista.
The G8x requires an external cable to connect the sound chip to the GPU, which is a crime so grave that it means any computer manufactures who do it can't put a Vista Ready sticker on the front of the box. Seriously, Nvidia? You put out your flagship graphics card and it's not Vista-ready? That's damn near inexcusable. One's just got to hope they'll learn from this debacle and fix their mistakes with the next generation of cards.