SPy looks really interesting! I've run across projects like MyPyc before, but as you say they kill a lot of the "joy" of Python by removing things like decorators and operator overloading.

One question, more out of curiosity than any genuine need: do you (or do you plan to) support any kind of trait/interface based polymorphism? E.g. it's a pretty common idiom to have a function that works on "any iterable type" and that sort of thing, which seems like it would be best modeled as an interface. I guess you could argue that's at odds with Python's tradition of "duck typing" but then again, so is static typing in general so I'm not sure.