I ordered a couple of these little mates just to try them out; I'd had a bit of a problem with the wing nuts in my cymbals gradually loosening during longer sets as well as the slight inconvenience of them falling to the floor or getting lost in between sets during gigs... Considering the price, these little babies offer a lot of comfort to cymbal set-up.
The locking mechanism makes it easy to attach and detach the nut, and also makes sure the tightness of your cymbals stays the same set after set.
The only criticism I can think of is that I can't use these with my Wuhan China: the force of the cymbal knocks the nut upwards so much, that I've had the cymbal mate detach completely during a song.