Had a try with this system today and what can I say superb results.
The car dried absolutley spotfree even on the glass without the need for chamoising !!!!!!!!!!!!!! and the shampoo didnt appear to strip of the wax either.
Well worth a try as they are selling the complete kit for £15 in Tesco's at the moment. The water deioniser refils are £4 each and last for approximately 10 washes so 40p a wash is more than reasonable.
In all honesty I can say that the car looked shinier than if I had washed and dried it in the traditional method and obviously the fact that your not having to dry the car will also help avoid swirlmarks etc.
Well worth a try in my opinion