Skinnable using HTML5 and Javascript or some simplifying wrapper. Specifically, I'd be after the effects possible using JQuery and HTML5.
I wouldn't necessarily expect a lot of media management options, aside from building/editing playlists. There are already tons of apps out there for managing MP3 tags, etc.
As long as the jukebox read all import tag formats and could utilize the data, that's key.
Also, being able to freely intermix Videos as well as audio, being able to stream vids from the internet (ie Youtube).
Finally, GOOD touchscreen control is essential, single touch is absolutely required, but supporting gestures and multitouch for some elements might be very nice as well.
For instance, JRiver Media Center has a GREAT 10ft presentation, but their touch support and UI fails miserably when actually used on a touchscreen.