Yep, MUI 3.8 runs fine on a 14MHz 68020. I think MUI was and still is the best thing since sliced bread in Amiga land.
I think it was a shame that it wasn't optimised more for 68000, but I agree it was pretty good for throwing together a skinable user interface.
It definitely wasn't for non-programmers. Although like any toolkit it allowed you to do things that you may not have had the specific skill to do yourself.
