Saw one of these being demonstrated and in the interval before the next performance had a good look at it - and decided to buy one. Only cost a fiver and another couple of quid for some spare bits.
I've done some heavy duty work with it - three inch number 10s into good wood, corrugated iron straight onto timber, garden timberwork.
Well impressed - but there is a knack - takes 1/2 a dozen attempts to get it right. The "gotcha" is the bits - they are NOT any standard size and even then they need a little O ring ... I bought a bitless one at a car boot sale (50p) and a friend to whom I gave it (having played with the complete one) is still trying to find a supplier of the bits and he has access to all sorts of specialist suppliers.
The build quality does look suspect - I'd love a really nice one. (Tool lust) Wonder who has the patent ... Barley Twist (Please put out the cats to reply direct)