yeah the expansion cartridge/module concept is pretty clever. i look forward to seeing what modules come out for it. feels like a video game console 
some cool things i’ve learned while beta testing:
• it’s a usb host, so you can plug in an op-1 or whatever if you don’t feel like playing on the tiny buttons.
• it’s a straight up 16 track midi sequencer with all sorts of cool sequencing tricks (step components, separate pattern length per track, sequence fx.) so you could completely ignore the internal sound engine and still have a capable and compact sequencing platform.
• you can control all of the internal sound engine parameters via midi