I've downgraded to the 5.x version to get it working again, but the ratings aren't there.
I use the ratings to give the songs that have crept into iTunes somehow that I really don't want to hear again a 1 star rating, have a playlist in iTunes that includes only 2 and more star songs in it, then sync that playlist to Android with isyncr.
Deleting the ratings.xml file from the symcr folder didn't help. Opening the recreated file shows that it's full of songs and their ratings, but Rocket Player seems to be ignoring that file. Maybe there's another place it looks for ratings.
I can live with it; it seems to keep and update to iTunes any song I rate again, it's just not syncing the already existing songs.