We just moved - into a house that is mostly carpet!!  With 4 (elderly) cats and two power chairs, we figured the carpet would be completely destroyed in short order.  Since hard surface flooring isn't in the cards for a couple of years - we did a bunch of research and settled on the Big Green.  Best purchase we've made so far, I think.  It is relatively easy to use (as carpet cleaners go) and the cleaning is comparable to the ones you can rent.  It has been about 3 months - we've cleaned the carpets twice.  Truthfully the hardest part is moving furniture :-P.