We kind of did the same thing before we bought our Dyson about 8 years ago. A friend had one and always raved about it so my wife borrowed it. We took our old vac at the time (I think it was a Hoover of some variety) and put a new bag in it and vacuumed the house carpet thoroughly. Went back over with the Dyson and filled the container in pretty short order. Went and bought the Dyson Animal (at least I think that is the name) and haven't looked back.
He had our carpets cleaned not too long ago and guy commented that we must have them cleaned often because the water that was being pulled out wasn't as dirty as he usually saw. It has been at least 5 years since we had the carpets cleaned. That is with 2 kids and 2 dogs in the house.