I won't argue against Windows 2000's usability. But I will say that to me, as someone who first started using computers in the XP era, any Windows earlier than Windows 7 looks so god damn ugly to me, and Windows 2000 even more so than XP.
Interestingly though, I don't have the same impression when looking at the old Apple OSes. To me, Mac OS 9 looks old, but not ugly.