I've tried TuneWiki, BTunes, and the Stock Music Player. I rank them in the following order:
1. Stock
2. BTunes
3. TuneWiki
I think the Stock player is still rated the best out of all the players out there. It seems faster, and although there's not much flair to the interface, it does the job, and it does it quite well. My biggest gripe is that it doesn't find album covers and so I'm stuck with a big ugly grey android as my album cover for many of my songs.
I fell in love with BTunes after I bought it. The way to skip a song by swiping left or right was great. My biggest reason for keeping BTunes is simply because of the lock screen controls. I hated the fact that with the stock player, I would have to unlock the phone first before I could change the song. BTunes lock screen player is amazing, since it eliminates having to unlock the phone just to change the song.
TuneWiki... ehh. It was cool at first, but the widget is horribly small that I can't change the music precisely. It has a great feature of adding song lyrics, which I thought would be cool, but then I realized that I don't really look at the lyrics after a while.