Originally Posted by Chris_W

BTW, going the other way (e.g., new 6700 levers with old 6600 brakes) can be made to work OK - just setup the brake so that it doesn't hit the rim until the lever has moved a little more than normal, but still far from the bars, and you get reasonably decent power and modulation. The cable pull ratio actually changes during the lever sweep with the new levers, which I believe Shimano call Servo Wave technology, which is why it matters where the bite point of the brake is.