I had an 8:25 ADR on 11/28. I always allow the extra time to use Disney transportation and we arrived at the turnstiles at 7:45. Now, it was a light crowd day, Tuesday in a light week, but we were let right in the ADR line and on up to the restaurant. We checked in at CP at 7:55 and were called with the first groups seated right at 8:00.
We saw my DD's BFFs, the 100 Acre Wood crowd, ate a yummy breakfast and left at about 8:55. We saw the stampede coming down the street, but we were in front of them, LOL.
That part was actually really fun. Looking back down Main Street and seeing all those people, while the other way - almost no one.
The restaurant was not full, but it did take 45 minutes for the characters to make the rounds. If you actually sat at 8:25, I don't know that you would be out in time for 9:00. But you may get in early, like we did.