October 2015 was the busiest October I've ever seen. Many days felt like Christmas, especially at MK and Epcot.
MK was best on a party day, which meant decreased park hours. Though in past years, daytime on party days meant a ghost town and that certainly wasn't the case this October. Mornings of party days uncrowded and pleasant up to about 10:30. It was moderately crowded from 10:30 to 4. At 4 the crowd level picked up significantly due to party guests entering.
The F&W festival was great the 1st hour. Then it picked up significantly. By night time, bottlenecks were common place around World Showcase.