I bought one at their stand at the Gadget show in the UK last week. I put it together right before my flight home and stuffed it in my bag. Right before checking my bag I noticed that the whole unit had gotten REALLY hot - like the batteries were being shorted out. I actually burned my finger removing them before it caught fire. Still, I figured better not to have a fire hazard in my bag during a transatlantic flight.
Of course, I had this new luggage tracking device and couldn't use it - and that is the flight where my bags mis-connected. Very frustrating. Will be contacting them for a replacement.