Peter
I have a few different machines I use to aggitate the chemical into the carpet and as I use microsplitters about 75% of the time aggitation is a must.
Using the Host,Sebo duo and Envirodry (e45) I find the Envirodry the better performer and like you Peter I also spend probably more time aggitating than wanding as it does make a much better presentation of ther carpet when its finished. On easy carpets that are not too soiled are are on upper floor and hard to access areas I find the duo is a god saver because of its weight and easy to whip round.I also find that spending more time on the aggitation I veryu rearly have to get on my hands and knees to remove the more stubborn spots.