> You aren't asking them to tweak a few things here and 
  > there to make a build go, you're asking them to make it 
  > fit a completely different system.

Precisely. Given this, is it such a surprise that Rust was initially written to use MinGW on Windows rather than MSVC back when it was an understaffed two-man project?

I should also note that porting to MSVC is a blocker for 1.0. It'll get done, we're just not sure by whom yet. Tell your friends: http://careers.mozilla.org/en-US/position/o3VZWfwD