Some things I saw in the Python 2.2(+.1c1) release notes ...
need to check if these apply to us also:

- If you try to pickle an instance of a class that has __slots__ but
  doesn't define or override __getstate__, a TypeError is now raised.
  This is done by adding a bozo __getstate__ to the class that always
  raises TypeError.  (Before, this would appear to be pickled, but the
  state of the slots would be lost.)

- The "pseudo-sequences" returned by os.stat(), os.fstat(),
  time.localtime() can now be pickled.

- pickle.py, cPickle: allow pickling instances of new-style classes
  with a custom metaclass.

- In pickle and cPickle, instead of masking errors in load() by
  transforming them into SystemError, we let the original exception
  propagate out.  Also, implement support for __safe_for_unpickling__
  in pickle, as it already was supported in cPickle.


