I use it if I'm on a bit of a blast, but most of the time it is off.
I find the artificially heavy steering annoying (why? You don't get any more response or feel, it's just heavier for no reason) and I find that I slip the clutch more pulling away as the revs go on quicker.
But when having a blast I don't mind the heavier steering (even if it is pointless) and I love the increased throttle response when blipping the throttle when changing down, fantastic!
Shame it doesn't affect the suspension. Sport spec with 17 inch wheels means great handling but hard ride. Be great to be able to just have the great handling/hard ride when Sport engaged, and a bit softer the rest of the time.
That said I prefer the handling to the comfort so don't regret the sport suspension.
I like 'em big...