I'm OS conflicted right now, don't know if that's even a thing. Currently using Windows 7, but depending on how good the newest version of Linux Mint is, I may use that instead.
A lot of them, I've been trying out the Phi with a bunch of different OS', Win 3.11 and a number of LFS cores and some other linux variants and a few Plan 9 but the plan 9 cores are actually booting through virtual PXE (qemu from a 4kb LFS system) so I don't think that really counts.