I've been liking the beta so far. I had some issues with saving files to livedrive, but that seems to be working so far. The only issues I've noticed is with importing some power points into easy worship. The odd time it would just not import and freeze up EW. The only fix I could find at the time was loading it into open office, save it out again, and volia! it worked after that.
As for MS betas, I love em! I've been using Windows 7 and office 2010 for a while now. I'm also in the Windows feedback program, so I get free copies of Windows 7 Ultimate and Office 2007 for sending back usage data to MS. I figure for $800 worth of free software, its worth sending a little data back their way.