I think they work great, if you know what you're doing. Going over the same area several times can result in too much thinning, particularly if you do it to the hindquarters area (don't ask how i know). I only use mine occasionally on his upper back and gently on his sides. More often i just use a brush to pick up the loose fur.
Now that's a good one, Traz.... a controlled shedding I Love it! (my husband doesn't appreciate the dog hair, so I have always tried to swiffer our hard woods every day... it's my concession to him not being the dog lover that I am... he'd be happy with a Havanese... tolerates my golden obsession with amusement) I am always looking for the next miracle and sort of hoped the furminator would be it... Oh well....
It's not something you'd want to use regularly. It's not supposed to replace a comb & brush. The furminator I think is just supposed to be used mainly during the big shedding times. I just got mine so I tried it out and it was able to get a lot of loose hairs out that the brush and comb didn't seem to get a hold of.
I use the Furminator at home on the Harley dog but only when necessary to get out the undercoat and never on furnishings or feathers....no tail either.
At the shop we use a similar tool manufactured by Andis, it is basically a Furminator that vibrates very gently. We have a Fur B Gone program that dogs come in for and many of them actually fall asleep when we gently use the Andis.
Moose gets brushed with his every other week. As long as you don't go at it like a meth addict with OCD it should be fine. I go over each area of his body a couple of times and he loves it. No signs of discomfort at all.
I also use mine every two weeks (sometimes sooner depending on my mood) and anyone is welcome to view the photos I have of Murphy, of course there are only a few right now, but everyone is welcome none the less.
I just go over his body a couple of times with a firm motion, and always avoid his tail, hind quarters, and leg feathering. It really has kept the fur in my home down.
The only thing that I have noticed is that I can't brush the same area no more than two good swipes, or that area tends to curl up when I blow dry him. Of course, this might just be the way that I am blow drying him, or he may be getting some wave to his new fur. Since he is my first dog, I am still learning. But I love my furminator!