Tried one in place of hand walking because there are a lot of stray dogs where I lived. Just decided to put my dog in a car and drive to the orchards where I didn't have to worry about it. The few weeks of e-mill VS the weeks of hand walking, it's really no contest. Especially for a hard pulling dog. If your dog will run one... I guess the only real benefit is that you can get one for free on Craigslist. I just got a bike instead and an attachment that goes from the bike to the dog harness or collar so I can hand both hands on the bike and just worry about steering. E-mill is like last resort to me from the work out, to the surface, having to modify it... If you bought a nice one you could've used that money on something a little better.