I think that says a lot about the fundamental power of dynamic languages in general and Lisp in particular. Plan 9 is in a lot of ways the zenith (or … heh … acme) of what C and Unix can do. It is awesome, it is wonderful, it is better in every technical way than Linux or true Unix. But it pales in comparison to the hacked-together incomplete Lisp machine that is Emacs.
Imagine how much better off we would be with true Lisp machines on our desks and in our data centres!
(in my ideal world this 21st-century Lisp machine would actually take a lot of ideas from Plan 9, and even some from Emacs)