I remember GEOS, but when I got my Commodore 128, it was only a couple of months before I discovered the "bigger computers." I didn't have my 128 for very long at all, but I had a Vic 20 and C64 before that. I thought the 128 was way better than my C64, but way too late. I wasn't much into video games, so that didn't last long. Chronology thing, I guess.
Berkeley Systems, of course, is known for BSD.