... also known as Whidbey.  People are starting to get this - some got it at VSLive/MDC, MSDN subscribers can download it now, and we're in the process of manufacturing and shipping media to alpha participants, MVPs and PDC attendees (should start showing up over the next week). 

This is not beta-quality.  We run weeks of tests prior to shipping a beta, and fix very little during that time other than major showstoppers.  This build in contrast has roughly one night of testing on it - we know it's not toxic but you'll definitely see ugly bugs.  We're trying to balance multiple considerations here - we don't want to stop the team just to get a build out, we do want to give people more frequent access, and we don't want customers to waste time installing a build that doesn't work at all for them.  For now, we think customers should install this only on a spare machine and only if you're ok with a “work-in-progress”.  We'll do more of these and as we get closer to RTM the quality will go up.  But for now, be warned :-) 

http://msdn.microsoft.com/vs2005 has some additional information on Whidbey, and we'll be posting more information specific to this preview in the coming days.  If you have comments/suggestions, please let me know.  Thanks!