Interesting one this. A couple of months after delivery of our new Jazz I had the rear discs inspected because of circular scores/grooves around the discs... and the rear discs never, ever 'polish' up to 'shiny' with use in the same way as the front. Unlike on all other cars I observe in the street, too.
So I phoned the Honda dealer and booked it in. (Interestingly my rear discs appeared to match the appearance of other Jazzs in the dealer's carpark.) The dealer checked braking performance and inspected the discs and assured me that all is to specification - "no cause for concern, sir."
I have yet to be convinced that my rear discs are, in fact, OK. I am concerned that premature renewal will be required at first MOT, if not before then.