I use Cython a lot! But mostly to speed up existing Python code, and build C-extensions faster. I don't see it as a strict subset of Python or a new language to build a community around. Nuitka I just started experimenting with to build standalone Python executable, and I really like the direction and roadmap they are following. In the end though both of these technologies seem like ways to somewhat speedup existing Python code and not attempts to introduce a strict language subset that would allow the greatest amount of optimization, and finally fix long running issues, like the inability to have multiple versions of a package installed.