Though new to 7 ownership, I can say my R400 K series which came with the CCRBs fitted, makes the engine very responsive. Compared to the Roadsport I drove before which, whilst quick, seemed slow to get going, this engine with the CCRBs behaves just like my last Fireblades (2 wheeled variety) with instant response and pull. The noise is good to hear but in all honesty, when you floor it while driving, other noises pretty much obliterate the induction sound.
I don't have a comparison of power before and after the RBs were fitted though I know mine was turning out 216BHP when tuned a couple of months ago, even though we found 2 cylinders had significantly leaking inlet valves (fixed now). So an extra 10BHP? Maybe.
I was getting 30 - 35mpg pre head overhaul, which to me is most excellent. I guess it depends on how heavy footed you are an how much you like the sound of the engine sucking in enough air to create a local low pressure zone.