It's one of my favourite things, looking at and analyzing older interfaces. Some are lovely, some are cute, some are ugly, but most are... "naïve"? I love to think about the effort, the research, the trials and tribulations. I feel I will spend a great deal of time in this page!
First and foremost to me those screenshots are somewhat disappointing as they can't match my memories. NeXT, BeOS, Irix, OpenLook, SunOS, Arthur (imagine the diversity)... they were SO awesomely impressive at insanely high multi-sync CRT resolution.
Reality simply can't match the mind's eye, at least not for me.
One that does seem to be an odd man out is Genera. What a concept.