Everything you write will be open source. No FASLs, DLLs or EXEs. Developer may want to have control over the level of access to prevent exposure of internal implementation, as it may contain proprietary code or because strict interface/implementation decomposition is required.
Ever heard of .pyc?
Probably the biggest practical problem with Python is that there's no well-defined API that doesn't change. This make life easier for Guido and tough on everybody else. That's the real cause of Python's "version hell".
Also not an issue, e. g. in Debian you can install multiple Pythons (starting with the oldest supported version; on my day job it is 2.5, my personal shit is 2.6) and test your software on all of them plus PyPy. Sure, you won't be using any good new features, but it doesn't even annoy me, let alone prevent me from doing my work.