I just had breakfast there last week. It was very good, the characters were great: Pooh, tigger, and eyeore walk around to the tables and piglet stays in the middle and you have to go to him. The buffet was good - waffles with tigger, pooh, and piglet on them, eggs, french toast, crossiants, donouts, fruit, omlet station - the usual for a breakfast buffet. If you like winnie the pooh characters I think it is definitely worth it. We didn't see those characters anywhere else in the parks (you pretty much see mickey everywhere you go), so it was nice for my kids to see them. I haven't had dinner there, so I can't help you with that.
As far as the time breakfast starts, we had a 9:00 ps and arrived at 8:40. They seated us about 5 minutes later. I don't know what time the breakfasts starts, but if you get a PS before the park opens you just let them know you have a reservation and they let you into the park. I always took my confirmation numbers with me just in case, but we never had a problem.