Ingo, why don't you just redirect people to the new location redirecting feeds to their new location. That way on some aggregators like rawdog you'll just get the updated URLs all set with no manual adjustments at all.

This post is also a hint that after deliberations I moved from planet to rawdog. It's neat and in Debian. Might have to try to write a plugin so I can read friend's livejournal posts with it too soon.