[Stubb]

I'm using compiled libraries for all my heavy lifting—the Python code is there to glue those libraries together in convenient manner that allows for exploratory programming. GIL-free CPython would let me distribute computations across multiple cores without having to deal with the overhead of multiprocessing (serializing objects across process boundaries, etc.).

[civility]

If your compiled code is thread safe, you can releae the GIL in your library and achieve parallelism with current CPython. If your compiled libraries are not thread safe, you can't get parallelism anyway.

Maybe, if your heavy lifting functions are very short lived, releasing and acquiring the GIL is holding you back...

Btw, I'm not defending the GIL. Python has enough visibility and significance to deserve a good implementation. It's just that most people don't realize the slowness of CPython itself is a bigger impediment to performance than the GIL. Python should be in the same speed league as JavaScript, but there are too many things hindering progress.