I'm by no means an expert on the subject, but isn't there an advantage to having a JIT compiler use LLVM?
On another note, I believe one thing that has been problematic for pypy adoption is that it does not automatically work with C extensions or Cython, and generally if someone already had performance issues with CPython, they would have written some C/Cython extensions?
It's a tool that allows you to write an entire interpreter in RPython (a subset of Python) and then have it build a native binary with a free jit compiler included, with the specifics of your language encoded within. The reference implementation for this project is a Python interpreter.
On another note, I believe one thing that has been problematic for pypy adoption is that it does not automatically work with C extensions or Cython, and generally if someone already had performance issues with CPython, they would have written some C/Cython extensions?