Oh and a lot of show people I know say treadmills can ruin gaits but I know Aleron uses one so I would ask her if that's a concern. The clients I had who worried were dobe (refuse any incline and only allowed to go at a certain speed) and GSD (certain speed and specific time).
Late jumping into this but I do use a regular electric treadmill for my dogs (got it free off of freecycle!). I have heard the same thing about running dogs on treadmills over the years - if they are not extra long, they will teach your dog to shorten their stride and that's bad. I have not seen that to be the case with my dogs, they are 18-24". Now if Roust gets much bigger, he may not fit on the treadmill
So if you have say, a big GSD that dog may not fit properly on a regular human treadmill to use. Otherwise, I don't think it's a huge concern unless that is the only exercise you are doing with the dog. Even if it does encourage your dog to change their stride on the treadmill, lots of things teach your dog to alter or shorten their stride like heeling, certain jump exercises, walking on leash with you, turning while running, etc. I know the Dog Trotter people are big on the "human treadmills will ruin your dog's gait for the ring" but then, they are trying to sell you a product.
Everyone gave pretty good advice on getting dogs used to it. I found with mine, it was best to put it on the lowest speed possible and get them jumping on and off that way instead of turning it on when they were already on it. And I don't see any issue with trotting Zinga on it at all. Roust has used it since he was pretty young. Obviously, you don't want to run an adolescent (or any dog for that matter) to exhaustion on it but I don't see the harm in them getting some exercise with it at all.