Oh I have many machines for different uses so got most of em, all from NG Morphos, AmigaOS4.x and classic Amiga OS/Workbench to ReactOS to Slackware to Opensolaris to all Windows versions from 3.1 up to 8 (have machines with era correct hardware for retro gaming since I like playing on real compatible hardware instead of vmware but use vmware also to check if my rips/copy protection cracking is working when I do copies of my Floppies/CD's to store em and upload them to a retro torrent community where I seed many TB a month), newer Windows OS'es are used for modern games and aplications that won't run under Linux.
On top of all that I got a big server that I am using for virtualization (EXSi), all from my webserver to ZFS backup.
And of cource I am running a machine with FreeBSD and pfSense connected to a 24 port HP gagbit switch to take care of my home network. Since my main server has a lot of capacity left I'm thinking of moving pfSense over there, tho the disadvantage of that is that the network will be vurnable for the exploits found in the virtualization software until patched, but no real big deal.
So got a wide spectrum and everything has it's use

Of all common OS'es I do not have OSX, got a PPC Mac Mini bud had no real use of OSX so din't install dual OS'es so only got MorphOS on it.
Have a good amounts of experimental OS'es also like ReactOS, mainly because it's fun

I got a Machine with Windows XP and Windows 98 also just because of eprom burners/programmers and other old/legacy hardware that won't work on new 64-bit OS'es.
Also have a huge Torrent machine used to seed tons of torrents (huge sets for all retro systems). Because of the I/O bugs in uTorrent I need to run multiple clients to be able to seed the Huge amount of torrents I have, as soon as I have a few TB of data in a single client the entire client starts to queue up until it stops all activity so need multiple clients, thinking of giving the uTorrent Server version for x64 Debian a go when I feel I have the time to move 20TB+ data and recheck on a new system...
As usual way to much text when I start typing haha...