Several people have mentioned rev hang on the 2 litre Duratec, Although when the 3.7 litre Roadster was introduced, rev hang was well documented, I have never experienced it on my 2011 +4.
I suspect it might well come down to something as simple as driving style
My understanding* of the reason for rev hang is that it's because the ECU is programmed to return to the defined idle speed (target rpm) when the throttle is released, but it does so in a way that eliminates unburnt fuel being allowed into the exhaust this is why revs don't drop instantly. Cars that do let the revs come down quickly tend to let unburnt fuel into the exhaust where it pops and bangs and messes up the catalytic converter.
This implies that if one has a large torque demand (ie Pedal position at a higher value than Throttle position) at the point the up change is selected, there will be a lot of fuel to be burned off before the target rpm can be reached, giving a rev hang condition as the revs drop slower than desired. Ensuring that the torque demand matches the new throttle position means the rev hang should be eliminated as there isn't excess fuel to be burned.
This certainly tallies with my experience, my car can rev hang like anything if I'm a bit heavy-footed, but if I drive a bit more sensitively it doesn't rev hang at all.
*This might be wrong, in which case I'd be very happy to be corrected.
