I always book these for 15 minutes after the restaurant opens then plan to show up 15 minutes before (we rely exclusively on Disney transportation to get from our resort to the park).
If Disney transportation is slow or delayed, we have less pressure to get there than if our ADR is right when the restaurant opens.
If Disney transportaiton is on time, and we arrive before the restaurant opens, we've found that we almost always get in with the first group.
So it's a win-win.
Moreover, if it's an EMH day or a park opens at 8, having an 8:15 ADR allows one of us to get FPs for one attraction while the other adult is checking us in to breakfast.
If Disney transportation is slow or delayed, we have less pressure to get there than if our ADR is right when the restaurant opens.
If Disney transportaiton is on time, and we arrive before the restaurant opens, we've found that we almost always get in with the first group.
So it's a win-win.
Moreover, if it's an EMH day or a park opens at 8, having an 8:15 ADR allows one of us to get FPs for one attraction while the other adult is checking us in to breakfast.