I've never had issues with FP either. Were we concerned with making it back to the park at a certain time? No, because we were quite forward-thinking. Example:
"Say, we have a Fast Pass for Space Mountain at 3. Should we ride Astro Blasters now?"
"No, it's only 10 AM. Let's go to the Haunted Mansion and we can ride Astro Blasters when we come back for Space Mountain."
Not hard at all. There have been countless threads on MC since I've started reading the forum and far before, I'm sure, about how simple it is to keep track of time. The same goes for MyMagic+. It's not stressful to figure out how to plan your day once you get constraints. It's probably easier because you work around some things and stay flexible. It's hard when you have all of these options in front of you and you have to plan everything you want to do without knowing where to start or end.