I've been running them for a couple of years and I'm really surprised when others say they lack power, I have to echo rj's comment when he says they can lock the wheel out almost instantly and in any occasion, I'm probably about 14st in riding gear and run 180 front and 160 rear.
Except for the rather major problems of having the brakes from the dodgy batch (the wrong material used in some internal components) which was sorted by Propel they've been faultless.