Yes, I've done the research before, and read their entire faq.. But their reasons are questionable at best, clearly designed to sell the product, not inform the consumer.
They say that dog hair building up on a regular treadmill is a problem, but anyone with any common sense cleans their treadmill thoroughly after each use anyway. And a little extra cleaning won't hurt anyone. Certainly not enough to justify spending $1500 on a special canine treadmill.. Of course, that's just my opinion. Not to mention quality human treadmills have sensors either covered or hidden to keep dirt and debris from building up anyway (human's aren't much cleaner than dogs).
They say that the side barriers keep the dog focused on the task. My dog would firmly refuse to step on the thing if he can't see all the way around him. Not to mention he may feel like he can't get away, which most dogs won't like. You can't force a dog into exercising without negative consequences, and most dogs are more likely to accept it and enjoy it if they don't feel trapped and forced to do it.
As for the extra padding and shock absorption, it's just as beneficial for dogs as it is for humans. A dog's joints and bones shouldn't have to take an unnecessary impact any more than a person's should. The extra padding may prevent repetitive stress injuries and hip problems in the dog's later life.
And if the treadmill you're using is unstable, you need a new one. It's just as dangerous (and uncomfortable, and disconcerting) for a person to run on an unstable surface as it would be for a dog.
There are serious flaws with every reason I've been able to find for using a specialized treadmill.. Most human treads have adjustable incline if you want to give your dog that sort of workout. And many human mills have a tread long and wide enough for you to run with your dog, which would be a comforting factor for most dogs.. The only exception I can see is if you have a giant breed. It would be difficult to find a tread with a long enough belt to accommodate the huge stride of a great dane...