Have tried the flappy paddles, and on the odd occasion will use them, but most of the time leave the car in auto with 'S' mode selected and rely on kickdown for a bit of acceleration (I have the 7 speed 'box).
What lets the flappy paddles down is that it is not a particularly fast gearchange, there is a slight delay when selecting gears with them. For a mass produced roadcar I would not expect lightspeed gear changing like an F1 car of course, but if the flappy paddles selected gears with just a little more haste I would certainly use them more often.
I will sometimes use them though, if only as a change to the norm, and a little bit of fun if nothing else.