I am trying to determine the maturity of PyPy by other means than reading the opinion of the developers. Therefore, I am interested in hearing about any high-profile mission-critical projects using PyPy. All other indicators of maturity seem fine. I am just missing this one before I decide on utilizing it for my main project.
PyPy has only just reached the stage where it is sufficiently mature to be a viable replacement for CPython in production environments where there are either no C extension modules in use, or those which are needed can be adequately handled via
Accordingly, there are not yet many examples of big migrations off CPython. There are however already examples of significant speed-ups in real world code just by switching interpreters - the most notable example I am currently aware of is LWN switching over to PyPy and achieving a ~67% reduction in run time for some of their Linux development data mining scripts.
Regardless, the key thing to keep in mind is that, unless you start writing RPython code, it is easy to switch from PyPy back to CPython 2.7 if you need a particular C extension module, or you want to target a platform that PyPy doesn't support.