Finally finished a script a couple weekends ago to synchronize data between Amarok, Rhythmbox, and iTunes. I now use Amarok exclusively, and it’d been bugging me for a long time that my old metadata from multiple machines and multiple apps was locked away and unexploitable. So i fixed that, for myself at least. I harvest everything into a common format and populate a big ol database with everything. Then I merge all the metadata together (averaging and adding, whatever, where necessary).
The code is ugly for now, so no public release. I might clean it up some time if anybody else wants it. Just ask.