I think i'm better off creating a topic by itself, as the current storm of people here makes things a bit chaotic.
There's a few things I'm just wondering about in curiousity, which I think only a developer like Dylan can answer:
The graphical content of the game, is it possible to customize this? I think support for Quest3D exists for 3D packages, unless you decided to make things harder here with specific fileformats? Reason I'm asking is because I would really love to see AudioSurf's environments become moddable. I'm a 3D artist myself and I'd really really, love to make some sort of environments for AS. You wouldn't even have to make things very noob-friendly if you ask me (actually i'd even prefer this to keep the quality of mods up, experienced people should be able to find their way with these things). And you probably also realize how much this could increase the fanbase and lifespan of your game (look at Need For Speed 3 & 4 for example, still going after almost 10 years...)
I haven't actually looked in to what is possible moddingwise now (can't even test with beta over anyway), but support for being able to choose your background effects when you play a song would be amust when this is possible.
And in terms of the actual graphical content: how is it controlled by the game? The gates get placed in advance i can see, but is there use of bones or anything for the car's pulsing engines, or the pulsating "space stations" for example ?
It's been asked before, bringing this game to Xbox. Whether you do it or not, i'm just curious if it's possible, as all your 3D is handled by the Quest engine, and you'd have to rewrite things with XNA? Is the audio-analysis code something seperate that can be easily transplanted to C#/XNA ? Anyway, personally I really think you should consider this (if you aren't already), the game would be immensely popular, you guys'd definitely make money off it and there'd be a lot more exposure. Too bad you haven't written it with XNA from the start actually (it's so easy to get something going with that).
Gamepad support other than the Xbox controller: my guess is the Xbox controller is there because Xinput setup was either easier or already included in the Quest3D engine? But is adding regular DirectInput support for "legacy" controllers that much trouble for you guys? I've actually done it myself in a C++ game project, so being the noob I am at programming I can't imagine this is that much of a problem/challenge?
Anyway, forgive me if I'm seem to be pushing on things, I know you guys probably have other things to do than work on AudioSurf all day, so I can see time is a limiting factor on most of these things

Hope you can find the time to answers my questions though!