It's "real" support, using your criteria. However, it's slower in PyPy than in CPython and than what the same thing based on ctypes would be on PyPy.

If there's a pure-Python version of the C extension, it might be faster on PyPy than the C extension support that cpyext (PyPy C-API compatibility module) provides.

Cython-based code is currently incompatible (it goes well beyond the public C-API), but a GSoC project to generate ctypes-based pure-Python code from Cython is (was?) going on.