Well on the Linux side I've still got JAMD installed.
On the Windows side of the street, I've used 3.1, 98SE, ME, 2000 and XP Pro.
My longest serving Operating System was Windows ME, I'd probably still be using it if not for the fact that Battle for Middle-Earth wouldn't run on it.
ME ran really quite well when the Optional Component Maker
BETA 10 was used to strip out all the crap that shouldn't have been put in there in the first place. On a kind of related note, I still use the My Computer and Recycle Bin Icons from ME on XP, I just think they are the nicest looking (the one good thing they swiped from 2000)