[ScottBurson]

Glad to hear you like FSet! (Not sure if you noticed: I am the author.)

I protest, though, that there's nothing about Common Lisp that makes FSet slower than Clojure. Rich Hickey used a very clever data structure called a Hash Array-Mapped Trie to implement Clojure sets and maps, and (I think) an Okasaki-style sequence implementation. FSet, in contrast, uses balanced binary trees for all these types. That's the source of the performance difference, not anything about CL.

What are your gripes about FSet?