I'm quite taken by the idea of the Hy-Rd, abd cost wise they seem similar to Ti BB7's. Other of this parish are sceptical because the Hy-Rd uses bakelite as an insulator to stop heat soak into the (very small volume) hydraulic reservoir and subsequent boiling. Bakelite is (only) good to 250C.
The following is from a recent review (UK based).
"It's possible to induce a bit of heat-induced brake fade if you drag a single brake down one of Bath's many hills and then try and use it to stop at the bottom, but it's fairly predictable fade and once you're using both brakes together it really ceases to be an issue at all. Even with a bit of fade you're still applying much less pressure on the levers than you would with rim brakes.
Heat transfer to the actual calliper unit is minimal. Even when the rotors are piping hot the hydraulic system is barely warm. TRP uses a Bakelite piston to insulate the hydraulics against the braking heat and it seems to work. I haven't tried firing myself down an alpine col in the high heat of the summer with these brakes, but I wouldn't have any qualms about doing so."
I'll be trying a set on my road bike when they become available.