I like that the poly aftertouch can affect the controller itself, rather than necessarily being sent out to an external synth. The one example i know of is changing the ratchet of individual notes in an arpeggiator sequence. Watch for a few seconds in this queued section of the Loopop video :
So this could be hooked up to a DIN MIDI synth, perhaps something very old that has no idea of poly aftertouch in MIDI and still do useful things with the poly aftertouch control.
I’ve been trying to think of other internal to the controller connections you could hook to poly aftertouch. Certainly note velocity ( the volume or accent of that note in the arpeggio ) could be connected too. I wonder about changing the length of those notes too.
ADDED : Looking at the manual it looks like maybe the length ( Gate Control ) of the notes in the arpeggio can be affected by polyphonic aftertouch. Pretty sure that it can. Not sure what that sounds like in real use though.