It would have to be either Windows 95 or Windows 98 in pole position for the worst OS I've ever used. Flaky, slow and cumbersome are words that often spring to mind when using MS operating systems.
Bizarrely enough I find XP to be quite good. Sure, far too many games won't work with it (Grand Prix Legends, sob!) but it seems generally stable and well thought out. Shame it uses so much system resources really.
AmigaOS (3.9) is responsive and easy to use but is now really showing it's age. The lack of memory protection and some cumbersome elements let it down, but this can be excused when you remember that the last THOROUGH revamp was over a decade ago. Neither OS3.5/9 are a true rewrite of the classic Amiga OS.
