We just went in February 2014 with a group of 9 and accidentally booked for Presidents Week (our kids here only get 1 day vacation so we had NO idea the crowds would be crazy until too late!). In spite of the crazy busy crowds, it was a great trip. We had temps in the mid 60's to low 70's except for one day it hit 80 (our World Showcase day, go figure!). It was pretty chilly in the mornings for rope drop, but perfect weather all day. We had one of our tireless teen boys who agreed to wear a backpack all day so we could wear hoodies in the mornings and stash them when it warmed up. The kids swam only on 2 evenings and the adults didn't brave it at all, LOL.
We also did the Backstage Safari tour at AK on this trip and that was really neat. We saw some great behind the scenes stuff with the animals and even met several close up including Nacho the food motivated hippo and a white rhino that scared the bejesus out of me (he wasn't yet on display because he didn't really care for people and that was very obvious). I know they have now renamed that tour and changed it up a bit though. My son was about to start college to get a zoology degree and his dream was to work at AK someday so it was very special for him. He asked a lot of very specific questions of the trainers and handlers and they were so great about sharing info with him.
Even with the crowds we had a great experience with FP+ (our first trip with it) BUT that could be because it was still pretty new and I don't think nearly as many people utilized it. For example, one morning on the bus to Epcot I changed all of our fast-passes around and had absolutely no trouble getting anything I wanted. I imagine you can't do that now, even in a low crowd time.
If you can avoid Presidents Week and the marathon week, you'll be great on crowds though.
