I've been to WDW twice in October - both times toward the end, over Halloween - and truly loved both trips.
Weather at the end of Oct is hot enough for shorts and tee-shirts, and for water rides, but the humidity is way down and the average rainfall is very low.
Crowds around Halloween are higher than September, but still way below the summer peaks. Most ride lines are 10 minutes or less (often walk-ons), restaurants are easy to get into without ADRs, and resort rates are Regular season at WDW and off-season low at off-site resorts. Airfare and car rentals tend to be cheaper, too.
I really miss October; I've been taking my WDW trips in December the last few years for MouseFest...