looks very interesting and looking forward to trying it out. Cairo: A Windows Shell Alternative - Home
I have to use Windows sometimes, and if it was with this software (if it ever takes off) then it'd be a much more enjoyable experience.
Unfortunately, UI hacks on proprietary OS'es never work out very well. There have been many in the past, but the problem is that with a monolithic OS that has almost no choices, software developers build for very specific scenarios. Have you used even a simple hack like multiple desktop applications for Windows? They're awful, since Windows simply isn't designed to handle that paradigm.