I’ve got the same problem.
I’ve bought a lot of audio apps like Lemur , Waldorf Nave, ims20, Animoog, PPG Wave etc and i just never use them …
Those are excellent apps but … i don’t know , for me the Ipad is more something to browse the web and listen to movies and stuff.
I have to stop buying apps really. If i didn’t have a Monomachine , Octatrack, A4 etc… i guess i would use the Ipad more but right now i just don’t need anything else to make music (except the next Elektron machine of course :))