Hi there, I've been using 0.3 for about a year now, and I have a suggestion.
Currently, I have 4 pi's running Rune for 4 different zones, and a 5th pi running a Flask server to control my amplifiers (I'll post my whole setup in the projects section when I get it up and running again this evening or tomorrow). In addition, the 'Controller PI' (the 5th one) serves up a sort of 'remote control' webpage that just has the basic playback controls (Play/pause, volume up, volume down, previous, next, and stop), and those buttons trigger CORS requests to the appropriate pi's MPD. I can post a screenshot when I get it running this evening if you want.
I think that serving that kind of a page for easy/rapid control of the music player would be really useful. Ex. if the phone rings and you need to pause the music in a hurry, the pause button on RuneUI is rather small and easy to fumblefingers, especially on a smartphone. I know you could just use an MPD client (kind of like I'm doing), but an all-inclusive option would be more polished/nicer. It could either be an overlay (i.e., a 'remote mode') on the main UI, or perhaps a separate page with a link back to the main page. You could also include it as a mode in the new Android app.
Just a thought, and I don't think it would be too difficult to implement.