The removal of cmp from the sort method of lists is probably the most disliked change in Python 3. On the python-dev mailing list at the moment, Guido is considering whether or not it was a mistake.
If anyone has any use-cases for sorting with a comparison function that either can't be written using a key function, or that perform really badly when done so, this would be a good time to speak up. -- Steven -- http://mail.python.org/mailman/listinfo/python-list