Okay how about: Shed skin is useless for real world python software.
It might make a useful tool for writing small subsets of python code for special purposes. RPython for example is not going to be adopted outside the pypy world becuase it's far less useful than Python for writing real code.
People put forth Shed Skin typically as a general python implementation, which it isn't. As a general python implementation it is useless, because it is not.