I don't have serious problems with any of the operating systems.
Mac, granted I used it for about a week but it ran fine.
Linux? Seemed to be fine I once dual booted using that one program (cant remember the name but it was on lifehacker) and I have used vmware and used ulteo a couple times.
Windows is the one I primarily use, but I do use some open source software such as Firefox (3.0RC1 to be exact)