magura, shimano, hopes all use to be IS mount. btw, the center lock to 6 bolt adapter is pretty slick, then you could run any brakes you would like. but if you don't like that idea the shimano brakes are great.
i have saint hubs f+r and run the 8" saint rotors (which i think look awesome) with hayes 9's on a 55 (post mount) with no issues. as far as i know you should be able to run any kind of brake you want, with the proper adapters. Are you worried about the compatablity with the rotors?
We have a winner, and by the way, I wasn't trying to be an ass about it.
Clearly there are going to be exceptions to every rule, but would you not agree with me that, generally speaking, a calliper is a post mount design? That is the point I am trying to get across. Hayes brakes are post mount, Avid's are post mount, for the most part, Shimano is post mount.
Snaked! I tried to post a picture of some shimano brakes that mount direct to the non post style. And even though they are older, there are a lot out there, and a lot of cheap copies. Setup sucks. You need to use shims to get them right, but then they are lighter and stiffer. But only by 1/2 a nano blivet lighter, for all the hassle. Hence the progression to better things.
But shimano used to offer all models of brake with the standard mount OR this direct system.