It is our belief that static virtual machines make very poor runtimes for dynamic languages. They constrain the languages to their view of what the "world should look like" and limit the options available to language implementors. We are attempting to prove this by writing an implementation of Clojure that runs on the Python VM. We believe that with a proper dynamic JIT (like pypy) a version of clojure running on a dynamic VM can outperform its JVM and CLR counterparts.
Aside from that, there are many Python libraries like PySide (Qt GUI), numpy, scipy, and stackless that do not have JVM counterparts, or at least the Python implementations are easier to use and learn. clojure-py will integrate tightly with thy Python VM and will be able to use all of these libraries..."