In case you have missed the link (I did, at first); this is Guido's opinion on the interfaces PEP as of March 7, 2002.
Jim Fulton has said that this PEP was premature. I agree. It introduces a new keyword, 'interface', and I'm not yet convinced that that is needed. On the other hand, the way this is currently done in Zope also looks butt-ugly, so something may indeed be needed. I think that at some point in the future when we have more experience with using interfaces (especially in Zope 3) we'll go back to this PEP and see how much of it we can use. Maybe there should be a special status "frozen" meaning not rejected but also not under consideration for the near future? But with a different meaning than Py-in-the-sky -- this PEP at least has lots of concrete proposals and studies the consequences.