I had one of these when I first got my dog but unfortunately I wasn't thrilled. I don't find them that comfortable to hold, and mistakenly hit the button and your dog is zooming ahead of you. Also, the button eventually breaks. I prefer to stick to nylon leashes.

Pros: Can length the cord

Cons: Can't mistakenly hit button

I have used this for walking my brit in the park. We walk a lot and he loves being able to go a little further ahead of me. It is nice because I can stop him when I need to with just a lick of a button. I don't trip over along leash. It is easy for me to manage.

Pros: durable and easy to use

Cons: none

Not only do I not like this because of a rope burn, I see too many people walking their dogs using this leash on a godforesaken celphone?!?!?!?!?!? Be responsible, the conversation is not THAT important not to be paying attention to your dog.

Pros: Great for lazy owners

Cons: can be a hazard to your health

I am not kidding I have had this for over 14 years and it has been great. Easy to use. The one I have has been strong enough for my poodle but I could see where you would need to get the larger one for large dogs so it would be stronger.

Pros: holds up well

Cons: could be a bit stronger

With smaller dogs it gives them much more range and freedom.
It allows me to let the dogs roam a bit.
I would not recommend this for dogs that are difficult to control and/or do not usually mind their owners.

Pros: gives dogs wider area to run and play while leashed

Cons: Not proper for dog control