I've been running Win 7 on my Mac Pro for six or seven months; started with the Beta, then the RC, and now have the RTM. I've got 10gb of RAM, and a separate dedicated internal drive for the Win 7 installation. I've only allocated 2gb of the RAM to Windows, and 1 processor core. Still, it's snappier than SL on some things, especially web browsing. I have no idea why, but Firefox under Win 7 seems to open most pages way faster than either Safari or Firefox under SL. It also seems to handle processing of large Excel files faster (although I realize that's likely due to the different versions of Office I'm using: Office 2007 for Windows, Office 2008 for Mac). At this rate I'll be slowly converting my Mac Pro to a Windows machine.