Hah.  This is a very good point, and one I'd somehow missed up until
now.  I don't think we *can* reasonably make equality comparisons
raise NotImplemented (in either 2.x or 3.x), since that messes up
containment tests:  something like "1.0 in {2, Decimal(3)}" would
raise a TypeError instead of correctly returning False.  (So the patch
I've put on the issue tracker is wrong, since it does raise TypeError
for equality and inequality, as well as for <, >, <= and >=.)