The machine Jonny is referring to is an oscillating pad machine, they work differently from an ordinary rotary. Look at the demo video he's directed us to
Theyt perform, differently from rotaries, although not as drastically different as the manufacturers would have you believe I don't think!
Whilst the dirty cloth looks impressive in the video, you could get a white terry towel almost that dirty just by wetting a heavily soiled carpet with water and rubbing it a bit! It doesn't mean there's no dirt left in the carpet, does it?
You'd have trouble convincing a huge section of the carpet cleaning industry that to get a heavily soiled carpet PROPERLY clean you NEED to use HWE. Bonnet machines are brilliant, I use them all the time, but in my opinion nothing replaces washing dirt away with water sometimes.
As with any method, product or machine there's a human factor involved.
You could put a right monkey on the end of a Hydramaster titan and he wouldn't be able to do anywhere near as good a job as a cleaner with 20 years experience using a single vac spotting machine.