i had a tenori-on for a few months when they first came out.
was really excited when i got it but soon realised how limited it was integration-wise and sound-wise. shame cos it’s got a good (if rather flimsy) interface. sold it for more than i paid for it though which was nice 
obviously it doesn’t come close to what the octopus can achieve (and apologies if i’m seriously duplicating what others have said) but it would be fun to implement some of the tenori-ons ‘two dimensional’ features on the octopus. the rotating 2D vector tracks (for want of a better description) and the vertically bouncing notes were particular favourites, and i’m sure we can all come up with some other modes that would fun.
or maybe i’m gonna have to learn how to program this thing… :dry: