Mr K,
I've done 2200 miles on mine now and she sounds the same as the day I got her, the glorious "howl" at 7000 rpm and beyond, is the same too.
I have the baffle in, as found her a little too loud with it out (have to consider the neighbours during her warm-up phase!)
As regards the demo bike sounding louder, perhaps demo test pilots just cane them from the off, possibly without proper warming-up or consideration for a cold engine? Just a thought.
Rob