Although R&B's are clearly dangerous if the circuit is busy with people who don't know what they are and aren't expecting them, I think there is actually a noise abatement benefit to them.
If I've got it right (and I've watched a fair few), fast noisy a/c belt into the drome and then kill the power and lose the energy with their high 'g' turn and hardly need to use the throttle again again until late final - this (as mentioned) saves fuel and time and it follows that the neighbours will have less a/c noise.
Also, I thought that the high 'g' turn was executed as a climbing turn? ie over the threshold numbers at 500' (often lower), climb and turn into late downwind at 1000'(ish).
The last two R&B's I watched were at Rochester. A swordfish, which pulled up into a fantastic climbing turn that had everybody on the ground gasping at the beauty of it, and a formation of a B13 and a Harvard. Watching the formation revealed why R&B's are favoured by military and formation pilots - I imagine that the following a/c was always quite confident about his leader's intentions and timings 'cos he could see him so well.
Steve R(1)