For me, Windows 2000 and Classic MacOS were high water mark of UI design. After that, change for the sake of change started ti creep in and then accelerated.

For me, Windows 2000 and Classic MacOS were high water mark of UI design. After that, change for the sake of change started ti creep in and then accelerated. Windows XP had the Luna UI with its Fisher Price color scheme and OSX moved to the lickabke Aqua UI.