I truly love this app, but I can still see room for improvements/additions. I'll start:
An option to have the half and double buttons latch, so you can audition different grooves without hearing them first at the original tempo.
Subfolders in the User libs, as deep as need be.
Drop-down lists of parameters that can be midi controlled, to match the list of midi ccs.
Master Start-stop under program control as an option.
Option to restart just the subset of tracks that were playing when stop was hit, rather than turning them all on.
Anything else? If any of these are already implemented and I'm just too dense to find it, please chime in...