I took a look at Songbird recently after aquiring an android phone (t-mobile G1).

Since iTunes won't sync it I was hoping that some open source solution existed. While I was very impressed by how far Songbird has come as a music player, the lack of sync options made me go back to iTunes :(

BUT, since songbird can use fancy plugins, maybe some smart person will realize that we need music sync support for non-ipod devices (and ipods too, I suppose) and write some plugins.