Interesting 'cause it's time for me to replace my growling rear rotors & I'm heavily leaning towards the Xbrakes because, at least as of today, money IS the issue.
My only problem, like some others who have asked, is that no one seems to know anything about this manufacturer. A quick search on Google brings up squat so I'm as leery as the next guy.
On the other hand, I don't track my cars so I'm not going to be beating the rotors. The majority of the braking occurs on those giant rotors up front. I live in the sticks & don't have to deal with too much traffic...........decisions, decisions.........