We've been in October quite a few times, both at the start and the end of the month. The weather is usually great - the main hurricane season has ended and it's still nice and warm but not as humid as during the summer (a bit like May really). One main draw for us is the Food & Wine Festival! Absolutely love it, and this alone makes October a great time to go!
Crowd wise it's certainly a lot busier now than it used to be but with a decent touring plan you still have minimal waits, and there are no problems finding 4th Fastpasses for the vast majority of attractions. The Magic Kingdom party nights are easy to work around. If you choose not to go to one of the MNSSHP parties you still get the benefit of a Halloween decorated park, which is absolutely beautiful.