Pull What, #86 is such a great post. Time is of the essence. That said, I believe poor management of it at every level is one of the airlines' biggest problems and, of course, other variables.
I was on this flight yesterday which pushed back early leaving behind passengers then flying real fast to arrive almost 30 minutes before ETA. Without any doubt they were burning more fuel only to wait for an open gate. This is why I have my choice over certain airlines.