Get your copy of Vista RC1
I'm using Vista RC1 on my main machine and it's working great. I would never go back. I even have SR configured to go through my TabletPC's array mic and have been using it for quick-and-dirty demos with no problems. It just works!
Get a free copy of Vista RC1 from Microsoft's site. You'll need to register for the Community Preview Program to get a product key. Scoble has more instructions for other ways to get the bits.
I see Long Zheng (of Vista SR demo fame) offers some instructions for how to make a dual-boot with XP.
While you're at it, get Office 2007 Beta 2 Technical Refresh.