[no_l0gic]

Nope, not any more: http://www.quora.com/PyPy/Is-Quora-still-running-on-PyPy (The answer you linked is quite old)

I'm even more skeptical now that I see a company tried moving to PyPy, and actually hired a core PyPy developer (Alex Gaynor - http://pypy.org/people.html) to make the move, and it still didn't work out.