In twisties or during aggressive braking, I rely on the front lever alone, to give me optimum proportional braking. They've never let me down. They are without a doubt the best brakes on any motorcycle I've ridden. I keep off the rear when riding aggressively in corners, since I really don't want a locked up rear tire steering me off the road.
However - I ride several bikes, with different break configurations, so I practice coordinated braking often. BTW, I really disliked the R1150RT fully integrated brakes for anything except straight stops on pavement.