Well they do good sponsor work.
Their gator grip is an excellent tool. I'd guess their chalk holders and bridge heads are just as good.
Their tips, especially the black variety aren't great, or at least they didn't used to be. Glazed over stupid fast. The clear tips do nothing other than make it more annoying for installers. People like the clear pad but I won't touch them. 2 installations were enough for me. It's a pain to trim them, even with a low end drill based lathe. I'd hate to see someone try to do so by hand.
Their gloves are junk, get tears after 3-4 weeks of serious use. A $2.50 Scott Edward glove lasts as long (maybe more durable) and works just as good. A 10 pack is $25, wear a new glove each week if you want, still much cheaper. Kamui is like Nike, a brand for those who like to wear brand advertisements around. I'm not hating on them for that, it's good marketing and a lot of people like that kind of thing.
Their original chalk worked well but was the most dirty chalk ever as far as the cueball was concerned. It basically tattooed itself into the surface. Their newer chalk... it might be good but I'll pass. I mean, I'd try it but see no point after going to V10.
The worst thing about Kamui was they normalized chalk and tips costing $30. I'm not super cheap when it comes to pool stuff, but $30 for a tip is pretty silly. That said I use a $30 Zan GripHard, but still stand by my opinion that $30 for a tip is silly. I promise I'm not cheap about pool stuff, it's just a little stack of leather and some adhesive should cost nowhere near $30. In the long run $30 isn't bad but they got the ball rolling on that, a good tip could be $15 and still be profitable.