Have really enjoyed reading through this thread. Instrument interfaces have been on my mind lately because I'm struggling to find one that I can commit to. It's possible I just can't commit and will always be reinventing ways to interact with my instrument. I've been working with a modular for the last two years, I'm almost exclusively an improviser with very little formal training. That said, I've devoured as much music theory as I can over the years, so I think I've got a reasonable base to rely on. I play some guitar and understand the structure of a piano keyboard, but I've never committed to real technique with either.
All that's background to say - one of my favorite interfaces is the Makenoise Rene. I really love conductive pads, and the configurability of "it's a sequencer that you can play like an instrument" is great. The James Cigler Rene videos really opened my mind to some unique possibilities. Especially his Rene 301 video,
I'm tempted to go all in and build an skiff around Rene and Pressure Points as my end all be all interface, but I waffle constantly. There's an aspect of my personality that likes breadth rather than depth, which is incompatible with the majority of musical interfaces throughout history.