After going through DOS, WIN3x, WIN9x, AQUA, ... I'm very fond of the early 90s model. WIN3, IRIX. I had deep lispiness before leading me to seek fully metacircular UIs with code as interface and interface as code (lisp machines, self, ST, node based Houdini/Shake) but nowadays, with a little more abstraction power grown by the years I really like the tiny GUIs I listed above.

Todays GUIs are stuck in some uncandy valley, too much css, not enough value.