I'm going to respectfully disagree with some of the PPs!
Other than EMH or a crazy holiday, Disney doesn't really tinker with the standard 9am Epcot opening. It's not like MK which does get moved around at times. Epcot is pretty set.
Second, while they do usually open the gates at 8:40-8-45ish for a 9am opening, they usually hold folks at a further point in the park until closer to 8:50/8:55ish. Then they let people go.
I have done several PPO GG ADRs and every time we've 1) had a great charachter breakfast which was a lot of fun, and 2) finished up in time to get my "head start" on the day (note, this may vary depending on what you want to do). Granted I do make it a point to eat, pay, and get going quickly, but it can be easily done.
Just my perspective!