Copenhagen,
In order to leave on time, you have to arrive on time. Just because the flight left late doesn't mean there wasn't a 20mi. turn round.
I have personally had a 16mi. turn round at GLA. The setup is good, with "captured pax" who don't wander off to the bar, duty free shop etc. all ready to jump in.
Generally the cockpit set up is not a problem so arrival time and disembarkation are the key.