girl, i made my hubby buy one for me last christmas. it is fabulous. we had red wine stains and coffee stains and chocolate stains and cat and dog puke stains, but that sucker zapped 'em right out! and mine is that super fancy hoover spin scrub model with attachments to do hard floors, and upholstery, so my kitchen floor at least has the potential to be squeaky clean.
it is loud as bejeezus though, so i can't run it if shoshanna is nearby. and i am a little concerned about the cleaning solution, but i guess it's a trade off between the filth we track into the carpet and the chemicals in the cleaner.
you are right, they are very expensive. but i figure we would have to pay big bucks to have the whole house done when we sell anyway, so it's paid for itself by keeping the carpets clean all the time.