I purchased the Cardio Canine in January 2007. I was interested in it because I wanted an effective tool to use when running with my dogs. It works great and I would highly recommend it to anyone who enjoys running and has a dog that they would like to bring along. I purchased dog harnesses shortly after because I found that the dogs would tire quickly because of the pulling on their collars. This adjustment only improved my experience. Most people would not need the harnesses as they are only needed if you plan to run with the dog. One concern some people may have is that they may feel they will not be able to control their dog is they allow them to pull. This is not true as the dogs focus entirely on the running in a pack mentality and do not get easily distracted by objects, animals, people, etc. I have had up to four dogs attached at one time and believe me that it is a great experience for all. The dogs go crazy when they see me grabbing their harnesses and head straight for the door. Highly recommend it and would love others to enjoy it so I won't be the only one that gets the strange looks from people when they pass by.
 
Sorry for the long note but you can tell I am a fan of the product and feel it is great investment.  Actually have had the dogs hooked up to me while I wheel a running stroller for my son so that tells you that they do not get out of control like some people may believe.