What is this info based on? The reason I ask is, for one flight today for example US Air has one estimated departure time and Flight Aware has another. Is the one on Flight Aware the one that is coded into the IFR Flight plan?
It appears you may need to read the Questions/Answers available at the top right of every page in FlightAware. It will help make your visits to FlightAware more enjoyable.
The short answer is that the times shown in FlightAware are wheels up/wheels down times, not gate times.
Yeah ok. Now I feel sheepish. Thanks for pointing that one out 
I raised this question some time back:
How is a flight listed as delayed 15 minutes if it’s already enroute?