One of the big goals of the project is to create a general tool for people to implement interpreters and VMs. The intention isn't to just provide a JIT vm for python, but to allow all sorts of new or existing languages to be (re)implemented easily. Don't be surprised if you start hearing about other languages being implemented in RPython.
I started one as a toy project some months ago (in April, tells me the filesystem), just for kicks.
I used ply to write the parser (aiming at 1.9.3, which has a lex/yacc parser), and that was the first time I leveraged a LALR parser, so it's very experimental, and as such code quality is lacking to say the least. Also, since ply uses (at least) kwargs, it won't pass through pypy build step. Still, early performance between cpython and pypy gives a clear edge to pypy.
To give you an idea of how much experimental it is, it's not even in my ~/Workspace (which is usually the step before github), but still in ~/Sandbox/pypy/pyby. I actually had a hard time finding it again.
One of the big goals of the project is to create a general tool for people to implement interpreters and VMs. The intention isn't to just provide a JIT vm for python, but to allow all sorts of new or existing languages to be (re)implemented easily. Don't be surprised if you start hearing about other languages being implemented in RPython.