I'm using it for my KH310 monitors in combination with the Neumann LH 28 on a K&M 26735 stand.
Very stable and secure on the stands, also makes it easier to align the monitors properly, rather than moving the entire stand for a bit of panning and tilting.
Also, I don't like moving my monitors around much, but sometimes I have to take them down when I'm working behind the desk. Always very scary to do, but with the brackets I can get a more secure grip on them. Just a little extra 'feature' of the brackets.
A bit expensive, but I wouldn't really trust any other alternatives. I paid a lot for the monitors already, so why not spend a little more on the thing that holds them up.