Has anyone ever used (played with it for more than just a few minutes) any operating systems other than the ones listed in the title?
I've used FreeBSD. OpenBSD, Solaris/OpenSolaris, Minix, DOS, Haiku, ReactOS, Android, Debian GNU/kFreeBSD, Apple ProDOS, Apple System 7 through OS 9, OS X, and there might be some others I can't recall at the moment.
I'm looking forward to Haiku, Minix, and ReactOS being developed further. I would love to run Minix on my server if it had better hardware support and more choices for filesystems. Haiku looks like it could make a great general purpose desktop OS. And for ReactOS, who wouldn't love to have a open source Windows compatible OS?
I really like Debian GNU/kFreeBSD. GNU on top of the FreeBSD kernel is great. I actually prefer a number of things about the FreeBSD kernel over Linux. If the Nvidia proprietary driver was compatible with it, and the Linux emulation emulated a newer Linux kernel, I might not even run Linux. I once ran TF2 under Wine in FreeBSD. It ran quite well.