Removing unbound methods also breaks the 'py' lib quite a bit. The 'py.test' framework handles function and bound/unbound method objects all over the place, and uses introspection on them, as they are the objects defining the tests to run.
It's nothing that can't be repaired, and at places the fix even looks nicer than the original code, but I thought that it points to large-scale breakage. I'm expecting any code that relies on introspection to break at least here or there. My bet is that even if it's just for fixes a couple of lines long everyone will have to upgrade a number of their packages when switching to Python 2.5 -- unheard of !
For reference, the issues I got with the py lib are described at http://codespeak.net/pipermail/py-dev/2005-January/000159.html