I'm one of those that believes you should book an ADR once you know that that restaurant is someplace you want to eat. You are always free to try and change plans and ADR's, but at least if you can't get an ADR for a different time closer to your trip at least you will have a back-up plan so you won't miss out.
Personally, we like the 1900 PF breakfast, but we like it more as a "brunch". When we plan on going we try to get one of the last ADR's for the morning (at about 11:20 or so). This gives us a chance to go to RD at MK, tour a bit, pick up a couple of FP and then head out to brunch. By the time we get back our FP's are usually in affect and lines are a bit smaller due to it being lunch time. We do sometimes pick up a pastry and juice or something before leaving the resort to hold us over until our ADR. This plan has worked out really well for us.