Ok... I still think WB3.0 is the best OS I've ever used. I guess I have a fetish of some sort :-D
Next best: FreeBSD. It was pretty hard to understand at first, but now I really like it. Logical and functional. I don't like the gui's that are available for it though. Or any *nix gui. They're probably very good, but any gui that isn't as comfortable as Workbench annoys me. I really hate clicking on things that don't respond immediately.
Worst by far: AROS. This is of course just a shameless attempt to annoy developers enough to work faster on it... Please tell me if it works. Can I please have a complete x86 native version now? I have a mini-itx system that's gagging for it :-D
Worst: Windows ME. Has anyone been able to find an OS behind the bugs? It cost me quite a bit of money, as I found that hardware was quickly accelerated upon trying to use it. Accelerated as in across the room...
Next worst: Windows 98. I'm using it now. It annoys me greatly. I get jumpy if I haven't seen a BSOD in a couple of days.