I've tried a few but none seem to be better than the standard app. All I want are:

1. The ability to bookmark (like the Karma)
2. A display that shows where you are in a playlist, e.g. track 1 of 399
3. Something that reliably remembers the last played position in a playlist. Sometimes it re,members, other times it starts at the beginning, a proper pain in the middle of a 90 minute podcast.
4. Talking of podcasts the ability to play podcasts through a playlist, I generally download podcasts and sync to my phone as a playlist.

If anyone finds something that does the above I'd be happy to pay for it.