I?ll throw in my two cents to say that I?ve used a fair number of GUIs over the years both
commercially available and FOSS, and I?d say that Windows 95?s UI blew the doors off of
anything I?d used up that point in terms of usability. Nobody IMO can fairly compare it
with the previously available X based desktops. The Mac was good, the Amiga was good, but
there was a lot more flexibility in how Win95 operated, and that?s probably why (along
with familiarity) that it has been so oft copied up to this point (Mac OS X?s UI
notwithstanding, which is also quite good).