Just tried to set them up on my Salsa 'con crosso but they would not work. They would not contact the rim with enough pad to prevent slipping beneath the rim with heavy braking. Ciamillo's solution was to sell me "sphereical washers" which did not solve the problem. Carbon TRP's work great now..
I have had the GX brakes on my bike for almost a year now. It took me a while to dial in the setup - I almost gave up, but now I love them. Turns out that it may have been my fault and not the brakes. The spring tension plates rely on a friction fit to hold even tension left to right. I got some grease on the back of those plates and could not get the fronts to hold even tension, so after squeezing the brakes a few times they would not pull evenly. The last time I pulled them apart, I cleaned them, put them back together dry and now they are holding in place.
I did not like the green swissstop pads that came with them; the squeal and didn't stop all that well. Now I use salmon Koolstops with alloy rims and yellow swissstop RX pads with my carbon racing wheels and both work really well. You certainly have to toe them to avoid squealing, but this can be done.
My current opinion of them after nearly a year is this: these brakes are light, look awesome and work really well when set up properly. In my opinion they are well worth the money.
I'm running a Seven Tsunami Ti with AlphaQ CX20 fork. Wheels are HED Stinger 6's, but I have also used my HED Ardennes C2 these are 23mm wide rims. It is just a quick cable and pad adjustment to swap between the two wheels because they are different widths. You have to swap brake pads too, so you don't ruin the carbon rims, but that is true with any brakes.
What setup are you running? Have you tried the GX brakes yet?
i'm running a 09 speedvagen, w/ alpha Q fork, mavic ceramic rims. No I haven't tried them. Just think they are a good looking brake, maybe one day. But honestly I don't think they would work on the rear of the vagen because the canti mount is designed around Paul cantis. Unless the zero G's can do like the pauls and pop the metal cylinder out for the "fatter" rear canti mount the vagen has