I've had mixed experience of this. On the one hand, given consumers in the US don't have EU261 protection unless they are on a Community carrier, there was a risk of being held hostage by the airline for hours on end, particularly during bad weather, and there comes a point when passengers should be able to draw the line on that. Before this rule was brought in, this was a genuine, if infrequent risk. On the other, the deadline has unfortunate consequences sometimes. I vividly recall being at DCA during a storm. After being held on the tarmac for 2 hours and 45 minutes, were were returned to the gate and the flight cancelled. It then flew empty to the end destination 30 minutes later. Had we stayed on board it was 99% certain we could have left just after 3 hours, but AA were not prepared to risk the fines.