We have gone a number of times in October. My observations :
1. It is usually still warm (we are from NY, so gauge what warm is to you). Early October still can hit 90, so we always do shorts, T-Shirts. We swim a lot in the afternoon.
2. Bring a sweatshirt for evening - usually not necessary for me
3. Crowds - They have always seemed very manageable to me. Disney is always busy, but not like the school break times at all.
4. Time Management - We use fastpass for the rides we really want - others are usually short waits.
October is great for us. We will be there the first week this year - F&W fest here I come!!!