Renting a Rug Doctor - Does it Clean Your Carpet, Or Make it Worse?

Have you ever rented a Rug Doctor from your local grocery or hardware store? If you have, you may have noticed they aren't exactly the cleanest machines in the world. I almost feel like it's doing more damage to my carpet than good. Who knows who rented the Rug Doctor before me. It could have been a serial killer cleaning up blood from his past victim, or a frat house cleaning up all the puke from the night before. That means that blood and vomit could be getting into my carpet. That doesn't sound like a chance I want to take.