Tried but hated the weedy loose feeling of low confidence when using midi/audio interfaces connected via the camera connection kit, especially on ipads 1-3. Worked but cables just kept on popping out.

Bought a behringer IS202 about a year ago and its been flawless. Sequencing via Monomachine works fine, charges while using, comparitively sturdy, midi + audio + battery powered + more. Sounds pretty decent, though I am sure the RME beats it, but for $180au its better than I expected.

I planned to grab the alesis dock but side by side the behringer had more, felt a little sturdier & also allowed sysex midi in/out(great for lemur, app editors etc).

I would love to see one built specifically for the ipad mini, maybe in time.