I installed it on one of my clean VPC Windows XP install (only had SP1 installed previously and no other software), and everything worked without a hitch. I will be putting it on my other VPC slices tonight.
I also tried to install it on one of my laptop's OS slices, and it failed. I now can not boot up that slice (when I do, it simply reboots itself). I had a little bit of everything on there, with XP SP2 RC2, SQL Server 2005 Beta 2, Visual Studio 2005 Beta 1, etc. It was in the process of installing the new service pack when everything froze. Not a big deal as I can easily reinstall a fresh OS. I did have a message saying I was running out of disk space (at around 180 meg) so that could have been the culprit, but I also wonder if there was an issue with installing the new service pack on top of all the other beta software?