APP is a very neat and useful idea, well implemented. I'm happy that I bought it while I could still afford it. ;-)
I think, though, that the +/- octave feature in QWERTY mode could have been more elegantly designed, for instance as clickable arrow buttons instead of a drop down. That is a nit pick, of course…
But a feature that is still absent but necessary, in my view, is a tempo clock with selectable tempo control! Many VI:s use more or less advanced arpeggiators and beat synced modulations as integrated elements of patches and they need a clock to work as intended.