Actor model concurrency is way more fun and easy to use than handling threads on your own. It's really nice to see this coming to Python. Let's just hope that this project doesn't get neglected like the one for Ruby.
I just discovered a very similar, albeit older project that essentially does the same (i.e. implementing the actor model on top of threads, greenlets or stacklets)
http://osl.cs.uiuc.edu/parley/
The most important part, i.e. the download section, seems to be down though.