DanHickstein wrote an answer about La Sportiva RT Ski Brake on January 3, 2012
It seems that the RT brake is a little different from the Dyanfit version since it attaches to the toe-piece instead of the heel piece and it can work in the tour mode as well. I think that part of the appeal of the RT is that it will come off in the event of a fall even when it is in tour mode. This appeals to me since I often bomb down short hills without locking the heel on my dynafit bindings and do worry that I might fall and destroy my knee since the binding is totally locked in. The RT seems to solve this problem.
I'm wondering if the brake makes it harder to step into the RT binding - it takes me long enough to get into my dynafit bindings without brakes.