Let's start with a little background on the FP+ system. FP+ has replaced the old FASTPASS system that had been in Disney for many years prior. The old system had guests rushing to pull a FASTPASS from kiosks located outside of ride entrances. You could only pull one FASTPASS at a time and would be eligible to draw another when the previous one expired. There was criticism around the old system as popular rides (such as Toy Story Mania at Hollywood Studios) would have you rushing as soon as you got into the park to grab a FASTPASS that may not be good until 5PM or 6PM at night.
Disney tried to improve their FASTPASS system with FP+. Now guests staying on Disney property will have the chance to book their FP+ times and rides 60 days prior to their arrival. You choose one park per day (even if you have park hopper tickets) and up to three rides in that park. The computer will give you several options for times that you can choose from and then you save your choices. If you are lucky enough to score FP+ times early in the morning, you can add additional FP+ selections from kiosks inside the park once you have used your first three. For this reason, early times fly off the shelf fast as well as FP+ for popular times and attractions, such as the meet and greet with Anna and Elsa right now. Hollywood Studios and EPCOT also employ a tiering system. You can choose one tier one attraction (think Rock 'n' Roller Coaster, Tower of Terror, Toy Story Mania) followed by two tier two attractions (think Disney Jr. Live on Stage, etc.). You can go in and edit / modify your FP+ choices as often as you would like which means you can keep your eyes open for an elusive time or experience if you weren't able to score that hard to grab FP+ early.
So, my take on FP+? The jury is out until I experience it in November. I like it in theory, but I'm a planner. I can see where some people will be irked by having to not only plan ADRs for a Disney trip, but now what times they want to go on certain rides up to two months before the trip. I wasn't able to get all the FP+ I was hoping for even though I logged in on day one I was eligible, but I'm not losing hope as I look just about every day to modify if something opens up. More to come on this topic in the future!