We do not want 360 people waiting up for the demo or having false expectations. The 360 demo will not appear on Marketplace tonight.
I'm still waiting for specifcs, but I'm being told that it's still in testing at Microsoft. From what I understand this isn't Microsoft's fault, and is more likely just an issue of timing.

I'm hesitant to give any estimates for a release, but I've been told it should be reasonably soon after the PC release, but could be as long as a few days.