Last night I got MonoDevelop working (to some extent) on Windows Vista x64 using the Linux binaries, tweeting my progress along the way.
UPDATE: In another 5am hacking run this evening, I've managed to build MonoDevelop fully in Visual Studio 2008, and debug at all the way to the Welcome Page, using 32-bit debugging on Vista 64. However, I'm going to have to tidy the project file fixes a lot before I commit them.