Benchmarking against other term-rewriting systems
There has been a competition (it's had three editions so far) among term-rewriting systems such as Maude, Stratego and ASF+SDF which you may be interested in.
It used a toy language called "REC" to specify some standardized benchmark programs, which were then automatically and/or manually translated into Maude, Stratego and ASF+SDF and the execution times were compared.
https://www.google.com/?gws_rd=ssl#q=%22Rewrite+Engines+Competition%22
I've used Maude off and on for several years and I really like it. Since its interpreter (written in C++) is open-source, you might also be able to get some implementation ideas for your Clojure term-rewriting system.
I studied Lisp many years ago, and only started studying Clojure these past few weeks, and I really like it. It seems like a good compromise between the power of Lisp and the practicality of running on the JVM - along with nice theoretical underpinnings such as persistent immutable data structure and CSP-style concurrency.