We just got back from a 9 day trip this past Sunday. Although we went during the slowest time of the year, the lines were long, even on rides like IASW and Spaceship Earth.
I was not able to pre-book any FP+ rides as the Disney My Experience (or whatever it was called) wasn't working for me. I tried multiple phone calls but decided to just wing it once we arrived because of the anticipated low crowds.
I think we just used the FP+ for two days. On one day, we used it just once for Soarin', and blew off the two tiered two tickets we were required to schedule. The second day, they were out of Soarin' tickets, and we could only schedule late afternoon time slots. We were in the mood to switch parks, so those went unused.
I bought AP's with the anticipation of returning within 12 months. I think we will try to do that to get our moneys worth (I had also purchased a TIW card), but I think it will be quite sometime after that before we return. It was very frustrating, and we are not the type to plan rides so far ahead.
I hope they really try to fix this system. Right now, it's a mess, with long lines for rides that were once walk ons (there are still a few walk ons), and inability to go on more than just a few rides a day. We did take advantage of the single rider lines, and the late magic hours did help.