I’ve seen Toshio Iwai perform on his Tenori-on and chatted to him and Yu Nishibori from Yamaha at ars electronica in 2005 (see pictures) – finally it will be launched – and luckily first in the UK, so I’ll try to get my hands on one asap. See http://www.global.yamaha.com/tenori-on/ for launch details.
Tenori-on with headphones
Toshio Iwai Playing the Tenori-on at Ars Electronica 2005
There are a few videos on YouTube to see the Tenori-on in action, for example this one: