The Sun NewS stuff was some kind of postscript based rendering system that ran in parallel to X with an X server sharing the screen -- kind of like how X works on MacOSX today). I stayed away from it because I used mostly X windows terminals & DECstations. There was very little Sun hardware I could sit in front of in my formative years as an undergrad in the late 80s / early 90s.
I kept the same basic customizations for years, mostly around focus-follows-mouse and what mouse buttons + key combos moved, resize, iconify windows. My problem was that the key things my muscle memory depended on were fairly hard to configure in most things, and by that time, it was too late to change my muscle memory.
Eg, I have this hard-coded in my brain:
Button1=m :w|f : f.function "move-raise"
Button2=m :w|f : f.resize
Button3=m :w|f : f.iconify
(this means alt with mouse button 1 = raise window to front, and move it, alt+mouse2 = resize, alt+mouse3 = iconify)
So changing to anything else that didn't easily allow this customization was painful. I used a Mac for almost a year, and lived in the X environment so much that I went back to a *nix desktop. I kept doing crazy thing when I moved my mouse to another window, and the focus did not follow the mouse. So I'd start typing code in an Xemacs window, and i'd be deleting or forwarding mail. Argh.