Well, I'm at least in the running for 'Shittiest' ones, through work:
Win NT 4.0 Server
Win2k server
XP Pro (all service packs)
Win 2k3 server
Win 2k8 server
Win 7
Linux
Unix
Solaris
And then Win XP on my laptop at home, and Win7 on my desktop. Some of those work ones suck, and yes, I interact with all of them on a daily basis. God, I hate NT at this point. When building systems and switching back on forth, things are just in the wrong places, harder, and lack of USB support kills me...