The way I understand it, Itunes is a tad proprietary, as is the media layouts on iphones/ipads.
For instance, I use JRiver Media Center, and they are pretty dang good about support devices, but there's a lot of noise on their boards that people report JRMC not working with one particular device or another. Apparently, something that apple does from one rev to the next breaks whatever they have to do to get access and play tracks off the device.
But I'm no expert on that so take that with a grain of salt.