What you have to bear in mind, a good machine in a Pro's hands, will result in an excellent job. A good machine in the laymans hands wont produce anywhere near the same results. Theres also much, much, more to cleaning a carpet and getting the desired result than just the machine. However a pure steam generator in the wrong hands can do a lot of damage to the carpet, and personaly I dont rate them as a useful tool in carpet cleaning. They are good at degreasing kitchens etc.
Dave.