As I bought a few tracks on the french iTunes Music Store, I quickly realise it was a dead end to use it in other players or in my MP3 jukebox. But hopefully there are great tools like the Hymn project that allows you to fairly use stuff you have bought on iTMS everywhere... It's very simple and efficient !

On other news I managed to correct a few AAC files I got from AllOfMP3 that had a buggy data at the end (from the PysTel encoder) using a conversion to Matroska :)