I have to turn the sport button in my Panda HP off in town traffic as it feels a little jerky, even with the slightest of touches on the pedal. On the open road I would consider it a sin not to have it on

I think other drivers get a wee surprise and the burst of speed when overtaking in the size of car that it is.
In terms of the MPG I have noticed that it only gets better with the engine having more miles on it. I'm on 22,000 miles and am recently getting average of 46.6 mpg based on the last 2000+ miles and that is with the sport button on the most of the time