Edit: I just found out that that the preview program is now FULL. Now it's time to go through the thousands of applicants. Thanks for your interest and good luck getting in!
Signup to preview the New Xbox Experience
Click here to fill out the registration.
Unattributed Quote:
Working with various teams across Xbox, weve developed a program to allow a select few of you early access to NXE. How do you get chosen? The first step is to head on over to Microsoft Connect, sign in with your Windows LIVE ID and join the "Xbox 360 Fall 2008 Preview Program" by clicking on this link, https://connect.microsoft.com/InvitationUse.aspx?ProgramID=2631&InvitationID=XBOX-G37M-QYWQ&SiteID=719.
Once you do that, you need to fill out the "Xbox 360 Fall Flash Preview Sign Up" survey in order to be considered for receiving the Preview System Update. We're asking a few questions about where you live, your home network, ISP connection and a few other pieces of information. We are looking for a good cross-section of our members in order to get the best feedback we can.
Let everyone here at XbA know if you get in!