When I bought the car (new) I was given the impression that the button altered the mapping from a milder 150bhp to a more agressive 170bhp.
Naturally I always had the button pressed from leaving my drive way so I never really gave it much thought.
Then I had it re-mapped (badly/smokey etc) and this actually disabled the button all together! So for 18 months or so I was convinced that the button ran off a watch battery and simply lit the button up orange, a great placebo!
Eventually, I had an epiphany and took the car to Gus who then made me aware of the problems and explained to me what it actually does.
It's been over a month since I last drove the car so my memory is vague on the feeling it gives, but IIRC, the sport button is more noticeable in stop start or slower speed driving.
IT DEFFINATELY DOES NOT CHANGE THE MAPPING!
On a side note, how much did you pay for yours Roswell? I'm looking at selling mine soon so trying to get an idea as to what it may be worth etc. (PM if you don't want others to know, it would be a big help knowing tbh).