i've tried a number of treat dispensing toys and so far this is the best. the material is a bit softer so not as loud on the hardwood floors, no dialing or adjusting for different size kibble, the dimples make it easy for the dog to pick it up and it stands up to my dog tossing it to get the treats out in multiples. washes easily in the sink. i let mine drain all day then take a paper towel, twisted to fit and insert it into the fill hole to wick away the last of the water before re-filling for more fun. i can't imagine having a dog without one of these - i'm planning on ordering a smaller one for the cat.
I bought one of the large ones for our Doberman and he loves it. He rolls it all over the house and only picks it up to bring it to us for refills. This is good, since it is definitely not meant for chewing.
I received the 5" ball as a gift and have used it for my collie and my boxer. The collie loves it but tends to chew on it, so it has several small holes. It will NOT stand up to much chewing, so close supervision is necessary. It does keep the dog moving and occupied for a while though. I bought the 2.5" ball for a cat, and she loves it as well. Chewing isn't such an issue for the cat. The one thing I don't like about its dispensing is that kibble tends to get stuck when there are just a few pieces left. This is good to get the animals continually going after it, but not so good when it comes to old kibble possibly getting moldy inside.