I bought one of these to try to help with the volume of hair in the house from our golden labrador.
Despite a thorough grooming once a week, along with daily brushes, the volume of hair in the house (and the hoover) was simply too much for comfort.
I'd been recommended a Furminator by a friend, and figured I'd give it a go. Wow. The volume of hair removed from the dog was simply amazing. Not only that, but he loved it, sitting there quite content.
I removed enough hair to fill a small carrier bag (had to compress it), and immediately noticed how much neater and more tidy his coat appeared (very healthy).
We now use it once a week, where it still continues to amaze me how much hair it removes, and we've seen a noticeable reduction in hair in the house.
A word of caution would be to not use it on any sensitive area (i.e. underbelly) where the undercoat is less thick, but for the back, sides, neck area (and tail) its a very very good product, and sold on Amazon at a very competitive price. I would also advise you to use it outdoors when possible, as the hair it removes becomes incredibly 'statically charged' when removed and will stick to everything (clothes, furniture, carpets, curtains etc).
I bought the medium version, and in hindsight should have gone for the large version, but this isn't a criticism of the product itself.