I now think the proposed changes wouldn't be bad thing, after all. I
have been bitten myself by the confusing naming of the Unicode API. So,
there is definitely a potential for errors. 

The main problem with PyUnicode_AsString(), as Marc-André pointed out,
is it doesn't follow the API signature of the rest of the Unicode API:

char *PyUnicode_AsString(PyObject *unicode);
PyObject *PyUnicode_AsUTF8String(PyObject *unicode);
PyObject *PyUnicode_AsASCIIString(PyObject *unicode);

On the other hand, I do like the simple API of PyUnicode_AsString. Also,
I have to admit that the apparent similarity between the PyString and
the PyUnicode API helped me to port my code to Py3K when I first started
working on Python core. So, pragmatism might beat purity here.