We mostly do our own grooming on a very regular basis, aiming for comfort and health rather than beauty, but every now and again will opt for the 'works' from a professional.
Recently, though, it seems that every dog groomer in our area is using a Furminator, and everyone seems to think they are grand tools.
But I hate them. Yes the initial effect is huge and dramatic and (with lots of sprays, I think) the groomer can present a lovely looking coat. However, I think that effect is short lived, and after a week or so the coat looks uneven, misshapen and even damaged. At worst, I though I could still see damage over six months later.
Maybe it's a breed thing. I am talking dogs with an undercoat, topcoat and distinct guard hairs, but maybe they work better on other breeds. I have never used one on another species, say a horse.
There are no professional groomers in my area who are not using them.