It isn't a slicker brush, it is a lot like a #40 clipper blade on a handle. I use the #40 to card the dog's coat (it gets rid of all excess undercoat after you brush out the bulk of it) Using the 40 is less comfortable on your hands than the furminator brush, but it also doesn't cost $50.. lol. You'd be AMAZED at how much hair I get out of dogs using that blade, especially dogs with medium-length hair and undercoats, like Labs.
As for the shampoo system, I suppose it's worth a shot, but I don't see how it would make that big of a difference. If you get your dog bathed well, and blowdried without any conditioner, the dead hair will fluff up and be easy to brush/card out.
I wouldn't spend my money on the furminator, but that's JMO.