I’ve had a Tenori-On for a couple of years, now: the cheap “Orange” one, made of plastic; not the metal framed “White” version.
After an initial period when I couldn’t put it down, I soon found myself disappointed that the volume of the device was too low for any kind of performance without additional amplification. There was also the fact that the Orange version could only be powered from a mains adapter, lacking the White’s battery compartment. (I believe this was purely to justify the price difference between the White and Orange – aside from the cosmetics and the lack of battery power, the two are identical in function and sound).