The absolute worst is American. I have flown it twice and both times I had 5+ hour delays on flights that were only supposed to be 3 hours total. One time they did not even offer anything to the people waiting. The second time all the passengers received $25 off their next flight with American.

The best is Virgin America. Never once had a delay and actually have left early before. Decent sized seats and in-flight personal entertainment. Plus Google maps as you fly which is awesome.