Not everyone thinks that such a thing would be bonware .
Probably shouldn't feed this any more, but..
I work primarily with Visual Studio and LLVM myself and have absolutely no objection to dropping VS2010. In fact, I stronly support such a move, as the VC++ compiler has improved quite a bit recently, especially in the context of the topical C++11 discussion. I don't want to assert anything strongly as I'm more of a LLVM consumer than contributor at this stage - I just want to provide some counterbalance to the XP support argument.
I can see why someone would not want to buy Windows 7. What baffles me is why sticking with WinXP (outdated, EOL operating system which is proprietary and will never be patched after april 2014) would resolve *any* problems whatsoever.
Any objections to perceived MS abuses would be better served by using any of the GPL or BSD operating systems or a competing proprietary OS. All of these choices can accomodate LLVM and Clang perfectly, and are arguably a more native habitat for them.