In and of itself, the Furminator is a very nice piece of equipment. Sturdy and well pieced together. Bit overpriced. It gets amazing amounts of fur off a dog too, with some caveats.
Overused it can murder the guard hairs. It's a hybrid, a cutter and a rake at the same time. If you understand a GSDs fur "system" a Furminator an be a very helpful tool, use it wrong and you can wreck a good coat. It's also sort of dangerous in that it's rather sharp and the wee little teeth can slash open skin.
A good groomer can point you in the direction of two or three tools used in combination that will do the same work in a safer and cheaper manner.
Never cook bacon while naked.