
We love them and have two here (twister and dog fighter), but.. their value depends on how you use them.
They are not designed for the dog to play with alone and I think thats something people dont realise sometimes, they are interactive, you and your dog play with them together.
The only time i use them other than this is with Dillydog whose only real pleasure in life is stealing - if he thinks hes WORKING for a reward he switches off (dont ask me why but in 7 years i have not figured out a way of directly motivating him for more than 10 seconds/1 repetition of something)..
To provide him with an appropriate outlet for his stress/reactivity, where he would normally go and look for something to steal, i will sometimes set him up to 'find' one of the toys, pre loaded with tastey foods. Because he thinks he found it and is stealing hte contents its super rewarding for him and hes NOT practicing counter surfing or fridge/freezer raiding..
Put it on the floor in the room im in and try to play with it with him and he just goes to sleep!
I still wouldnt leave one (even the new plastic versions) with an unsupervised dog, either they wont get the benefit of using their brains to figure it out, or they will learn to get the treats out in an inappropriate way (one N.O. toy slung at a window or wall or tv does a fair bit of damage i would imagine, and i do have dogs sufficiently into brute force and ignorance type approaches to problems to do that!)