Oh this is a funny topic; I just found myself looking for a decent music player on linux like a month or so ago and the situation was... disappointing.

The nicest looking one I could find was amberol, but that was a bit too minimalistic for me. I like minimal UIs but that doesn't have to translate to minimal feature sets as well.

But in the end I didn't find any simple but hackable players that I liked; in the end I just settled on audacious because it's just simple enough in terms of UI and good enough in terms of features. I do like the playlists as tabs idea though.