Hi Paul
I to bought a thermadry system last year. At first I could not get on with it at all, I even had Jason from Craftex come down come down and clean a carpet with it to see where I was going wrong.
Now after using it for some time I am getting very good results and am very pleased with it, I even cleaned a trashed bw in a chip shop restaurant with it the other day, the traffic lanes were black with chip fat from the kitchen, to my amazement it come up like new!!!! (It was so dirty I used 5 pads both sides to clean an area of about 30sm)
How i use it is - First light mist with MS then a really good long scrub. Wet the pad in Catalyst and squeeze as much moisture out as possible. Put the heater on and move the machine quickly over approx 15-20 sm of carpet to evenly spread the Catalyst and to heat up the pad. Move the machine back to the beginning and start the cleaning process, I move the machine back and forth then side to side, Keep an eye on the pad when it is soiled filp it over and carry on, then change the pad as and when. Once the whole carpet is done i the put a dry pad on and quickly move the dry pad over the whole carpet (20+sm) doing this i find really helps dry the carpet super quick and also pick up more dirt left behind. The trick is is to get the pad hot as possible when spreading the chemical so when you start cleaning it is hot.
I Hope this helps, I have to say I mainly use it on med to low profile carpets and am now getting very good results. I do still use HWE on about 50ish% of my work but it deffinatly has its place.
Regards
Duncan