It arrived today.
First impression: Extremely light and compact, but it feels anything but robust. Even my Seqtrak feels like a tank compared to the Nanokey Fold. I doubt that the hinges will survive a fall from table height if the device is unfolded.
Regarding the membrane keys: They are quiet, have to be pressed quite firmly and have a noticeable click point. Due to the relatively high force required per finger, you can’t really play them smoothly. The best way to “play” the keys is with the index fingers of both hands. Chords that you try to play with one hand become strums. Double triggers also occur frequently.
Great idea, but not for me.