the GIL was not removed or at least a solid parallelism story was not included
Not for lack of trying. People have been trying to do this since at least python 1.4. They just haven't found a way of doing it without negatively affecting single threaded performance, which Guido considers an unacceptable trade-off. http://pyparallel.org is probably the most interesting latest experiment in this field, but it never got cross platform support and seems to have stalled out.
The C api isn't the blocker for removing the GIL. The blocker is that Python is a dynamic language and there is no good way to know if another thread has just changed the underlying function on an object or not without having fine grained locking.
Fine grained locking works, but is expensive for non-multithreaded applications and slows down Python. It would speed up multithreaded applications though.
They did break all C extensions in py3k -- not so bad you can't work around it with some preprocessor magic but break it they did.
And they continued to break them within the py3k lifetime, mostly unicode related stuff from what I can remember. Probably still break stuff but I haven't had time for my toy python projects in a while so haven't been messing with the C-API lately.
Not for lack of trying. People have been trying to do this since at least python 1.4. They just haven't found a way of doing it without negatively affecting single threaded performance, which Guido considers an unacceptable trade-off. http://pyparallel.org is probably the most interesting latest experiment in this field, but it never got cross platform support and seems to have stalled out.