I'd ridden a few at work before I bought one.
My first one was new in early 1989, a 100GS in black. At that time I had an '88 K100RT, the GS was a second bike.
(Look away Keith).
I bought it mainly for the Para-lever. I ordered it on the basis of the write-ups, all very complimentary and before the local dealership had even seen one.
Compared to the K, it still felt as though the wheels were connected with a rubber rose-joint somewhere in the frame. I kept it about a year and sold it.
A while later I sold the K-RT and bought another black 100GS of about the same vintage as my first one from Newport. It had a few more extras than my first one and I kept it for years, did loads of miles on it but got fed-up with wringing its neck all the time, something that really didn't suit it.
I p-ex'd it at V&J for a red K1, set off around Spain on the K1 for three weeks and I have to admit, on seeing lots of great trails in Extramadura wished sometimes I'd kept the GS.
I always wanted a PD but they wouldn't import them because of the plastic tank.
I may have kept a PD and when I bought my current 1150GSA, I toyed with the idea of buying a good PD instead.
In retrospect, I'm glad that I didn't.
I still love the Two-Valve Boxers. I'm lucky that my mate re-acquired his old 80/7 and I got to restore it, thereby enjoying the simplicity of the design (I still do the 'fettling' of the 80/7 but I don't rule out the possibility of getting one myself one day as a project).
I wouldn't own one as an only bike at the moment simply because I don't think they're as good as the 11XX's for what I want from my main bike.