Honestly, this is my personal favorite time to go.
The weather will just start cooling down for Florida. So, shorts are definitely in order during the day, but you might want a sweatshirt/sweater for the evenings. It's 50-50 at that time if you will need it, but always good to have the option.
As for crowds, traditionally, this has been known as an off time. But, with F&W at Epcot and just general crowds, there really aren't any major down times. If you are used to going over holidays or the summer, you will notice a marked improvement. Other times of the year, it will feel about the same.
Also check park schedules. Several parks have different hours during the week, so plan accordingly if you want to maximize park time.