It lasted only a week. I had Vista Beta 2 and Office 2007 Beta installed on my laptop (my primary machine.) Everything was fine (besides my machine running a bit slower) for a couple days, until .NET 2.0 decided not to let me debug code anymore. It was strange, all of a sudden, all breakpoints I set in code had stopped working. I was going to try reinstalling the .NET Framework 2.0, but it's not an option with Vista since it's "baked" in the OS. So I tried reinstalling Visual Studio 2005 in an attempt to fix it with no luck. Since I didn't want to take the chance of this happening again, I just decided to put WinXP back on my laptop.
Now, why did I install Vista Beta 2 on my primary machine? Well, it's the only one I have that can run Vista (too bad the graphics card sucks, so Aero wasn't enabled.)
Well, I wont be installing Vista again until after it RTM's since I don't plan on buying a new pc until after that.