Unfortunately I have to report something negative about Windows 7. Running in a VirtualPC VM on a machine that does not support hardware virtualization makes it next to impossible to do anything meaningful. It runs (depending on your definition of running) but it is incredibly slow to start with and freezes up completely when trying to debug something in Visual Studio. I doubt it is any one of the technologies on their own. Windows 7 on a new'ish machine runs very well and Visual Studio debugging...
Today I'm just starting to report on my move to a Windows 7 development/testing environment for BizTalk. I'm happy to report that all the prerequisites seems to install without issues - as probably expected. These are VS2008 + SP1 and SQL2008 + SP1. To make sure I'm not breaking by current environment I'm installing everything into a Virtual PC first to test that all my tools and stuff works together before trashing my main OS (WinXP still). The only 'interesting' or scary...