Well, I think it also depends on the airports you are dealing with too. I did have one less than pleasant experience with Delta at the West Palm Beach airport. We got to the airport 25 minutes before the flight was to leave and they wouldn't let us on the plane because it wasn't 30 minutes. So, we had to rebook. It worked out well because it only cost us $25 per person more to take a later flight. The guy that rebooked us told us to call back a hour later to get the $25 per per deal or otherwise it would be $100 per person.
I was a little pissed at first, but it wasn't their fault that we weren't at airport on time and only $25 more made me feel much better. Maybe they aren't perfect, but I'll still stick with Delta.