I have a large, long haired monster cat with Maine Coon origins, he had developed massive knotted mats of fur that I simply could not remove with any of my other grooming tools, I had been warned that shaving was the most likely solution. Well, I wasn't happy with that so I bought the FURMINATOR and I am so glad that I did. It removes so much fur in one swipe that you will be wondering if your cat will end up bald but this is all the loose fur that they leave all over your bed, clothes, carpet or wherever else they sleep. The one issue that I wasn't entirely happy with was the static that was produced, after 3 swipes I had to dump the accumulated fur or it started sticking to the brush and then to me, I ended up covered in cat fur but I really didn't mind this much since I was on a mission to remove my cat's matted fur without hurting him, he had 6 very bad knotted mats and it took me 4 separate brushing sessions to remove them all (each session lasting between 3 to 7 minutes depending on how hard he tried to escape) so not a great deal of time in total, this is compared to over an hour of trying to detangle his fur with various other grooming tools (specifically designed for this purpose) which just did nothing to help.
My conclusion is that is you live with a cat you really need a FURminator. This review is written about the large cat/long haired version but it works equally well on my smaller, short haired cats so if you have a mixture of large/small/long hair/short haired cats I would recommend this brush to you rather than the smaller original version which will be fine for small cats but not so great on huge ones.
Please do remember though that when trying to remove matted fur you MUST hold and protect the cat's skin while combing to prevent the fur being pulled out in clumps (and possible mutilation of your hands and face by your enraged feline). This may necessitate you having an ally in your de-furring adventure, one to hold the kitty and one to wield the comb.