I already did my compliments for Loopy... great app!!!
Now, after some week of use, I have some little suggestion:
The orange control bar is very nice but I find it that the horizontal scroll (on the short side) it is very hard to use and the thing that it's a never ending loop (at the end it start again from the beginning) doesn't help. Personally I think that the main controls (play/pause and tempo) should always be visible.
In alternative... to leave the aspect of the app very similar to now. The control orange area could scroll vertically (on the long side) with the main and more used control at the boundaries so that we can go quickly (i.e.) to the top to find the play/pause/tap/tempo and to the bottom to change the length of the loop.
I think that the "group" thing will be very useful. I don't know if you are planning to add it (I can't figure out how to do it in a simple way), but in the meantime I think that you should allow to assign the same midi event to more than one action (with a warning, maybe). If I can Mute on/off multiple tracks with a single midi signal I can easily manage complex structure of songs (verse, chorus, etc.) without loosing the easy of use of Loopy.
I'm a professional musician and I have to do an hardware review (in italian) of the Tascam iU2... I decided to use Loopy as software, I'll let you know :-)