Highly recommended. Easy to install, the LED module replaces the existing bulb and the switch replaces the standard end-cap.
Compared to a standard Mini Mag the light from this is much brighter and whiter and battery life is extended.
Not cheap, however, so for professional use look at the LED Lenser range. Note that you also lose some focus capability and the ability to use the torch as a candle, but you can always put the old bulb back in for this. Also I'm not sure about the switch modification, but you don't have to use this.