We were also "super users" of the old FP system, and we enjoyed those trips very much. We would leave the park for our break with several FP to use later in the evening. My son wanted to ride ToT ten times on his tenth birthday and that was possible. Our last trip was in 2013, before FP+ started but after they were enforcing the return times. We did less repeat rides on our favorites, but we still had a great trip. We found that we spent more time in the pool or at the water parks in the afternoons, some evenings not bothering to return to the main parks, but it was fine.
Our first (and likely last) trip with FP+ is in June. We haven't made our FP yet, but I think I know what we want, except for MK. Our kids are older, and the list of things they want to do in the parks is much smaller. We are planning to do the parks from RD until lunchtime, as always, then hit one of the water parks after lunch most days. We will return to each park at least once for the nighttime shows. We have 2 days in each park except AK, and I am thinking that I may schedule some of our FP for the evenings.
I am not sure we will like FP+, but I'm trying to keep an open mind about it. My biggest issue is know what times to book them. There are some advantages, such as knowing we can sleep in if we have FP scheduled for later in the day, or possibly going to a water park until they close and then going to a park with all of our FPs made for the evenings,