The stock app shows a list of songs. When the music app is showing swipe from the left to the right to add music to play.
Swipe from the right to the left to see a list of songs in the playlist you made by picking with the earlier swipe (best I remember, its freezing cold outside and raining so I'm not going to double check this right now
).
The only thing that bugs me with android players in general is the way it handles random song playing. When set to random going up or down track wise does send you to a random song but you cant go back to the last song. Its a new random song no matter what. VERY annoying. I haven't had time to find a solution to that yet.
Sound quality with the sd card like you mentioned is awesome. It was like installing another amp and speakers compared to the stock setup. Its the first time in hundreds of radios I haven't changed the eq, bass, treble, or anything on from out of the box. It just sounded great.
It does seem to filter certain bass notes in a way that makes me think its being redirected to the sub woofer output. Its a clean cut out of that sound range. I cant wait to install the jl audio sub to find out of that is what is happening. If it is this is going to make a great SQ level sound system.