I've settled on using both MixZing and the stock Music Player for different functions.
MixZing I like because of the recommendation feature. I don't normally use a desktop audio solution much, when i'm at work I usually use Pandora so I don't have any playlists nor do I take the time to create any. I've found Apple's Genius ok and MediaMonkey has some solutions but I don't like any of them as much as MixZing. I also like how you can create a "Playing Now" list so that you can continuously build a set of songs to play that aren't a part of the playlist feature. It's very powerful due to the fact you can do it from almost anywhere including Genres, Albums, Artists. I also like the information on the artists though I imagine after looking through all of my artists this would eventually lose it's appeal. Lastly after the last update the video player now works.
Stock Music Player I like because of the fact long presses gives you a lot of nice options including going to Amazon MP3 store. With Pure Music widget it gives you great options from the home screen so that you don't need to go to the actual program. Pure also gives you so many skin options it always fits whatever theme you are going for with your phone. I also like the way the stock player sorts artists so that after an artist is it quickly shows all their albums without going into a new screen. I know this seems trivial but it's nice not having to go back and forth between screens like other players when you want to look at Artist>Album. Really wish the stock player had a Genre sorting feature. Last thing I like is that it has the playing now always at the bottom of the screen while looking through the tabs of artists, albums, songs, and playlists. I know it also seems trivial but I don't think MixZing handles this well. The Menu click to playing now is always in a different location depending on which subscreen you are in for MixZing.
So what I actually do is use MixZing for creating playlists and then the Stock Music player for normal music playing.