If "played with" counts as "used," then I go all the way back to 1.0 (or maybe it was 1.01). Also played with OS/2. I always had a "play machine" in my shop at home, so I could try anything new that came along. When IBM foisted the PS/2 upon us, we bought two of them at my company -- and never, ever, bought another IBM PC. Non-IBM PCs regularly came with Windows disks included. I always snagged a set if there had been an upgrade, but usually somebody in Accounting would peel the labels off and re-format the disks for general use.
Windows 3.0 was the breakthrough, and almost, almost, got it right. Windows 3.1 was the winner, then, of course, Win95. I have owned and played with at least one copy of every version of Windows since the beginning. Just for fun, the same is true of MS-DOS, clear back to when it was PC-DOS, and even Apple DOS & CP/M before that.
Windows 2.0 was I believe my first Windows OS, but didn't use any full time until Windows 3.1. I hung on to DOS due to speed for some time and then in college worked in unix since the workstations the school had were so much faster than the 286 (this had a full MB of RAM, a 10 MB hardcore, and a 3.5" floppy drive) in my dorm room. I've used every Windows OS from 2.0 to Windows 8 with a few others thrown in the mix. Windows 7 actually kept me from installing OSX on my netbook when Windows 7 was still beta. I'm really liking Windows 8, but do think it is going to take sometime for people to adjust. Most people just do not like change as much as they like to claim they do. My favorite OS of all time is still BeOS (Sorry Microsoft and Apple, but BeOS was amazing).