I've just installed Microsoft's Virtual PC 2007 with Ubuntu running as a VirtualMachine, and its all going pretty well for a first install....so much so, that I'm typing this inside the Ubuntu VM! I've been testing the java version of Minus4 and it runs pretty well here, of course this is a pretty big machine (quad core, 4gig ram etc.) so its not a big surprise... still, at 50fps its pretty solid.
Once you scale the screen it starts to get sluggish, but a single frameskip pushes it up into the mid 40s and another to an solid 50. This is fine for games like mercenary that didn't draw the screen that much - or even XeO3 as I only draw the screen every second frame.
I still have to get sound working - and get the screen res fixed as its currently locked to 896x600 for some odd reason. Once I've done that I'm going to try and get mono installed ready for some real work! Then I want to get a Mac VM created (if possible) and try the same stuff there. This would give me a solid development platform and let me do ALL my work from a single machine/desktop! How fekin' cool is that!