The outcome of discussion of this issue on python-dev was that the
lookup methodology for the special methods needs to be better
documented, especially for those cases where the instance *must* be
bypassed in order to avoid metaclass confusion for special methods that
apply to both types and instances (see issue 2517 for such a problem
that currently afffects the lookup of __unicode__). However, we're not
prepared to add a standard delegation mixin to the standard library at
this stage (I may still add a cleaned up version of mine to the SVN
sandbox as an executable reference source for the relevant section of
the documentation though).

While I offered to write that new section of the docs during the
python-dev discussion, I'm not sure when I'll be able to get to it (My
Python time lately has mostly been spent investigating __hash__ fun and
games).