We visited October 8-13, 2012. Granted, all of our 6+ prior visits had been during Easter break (which is insane), but we were delighted with the lower crowds. (By Touring Plans' reckoning, I think the levels were around the 3-5 range, out of 10, during our visit). Half of the attractions were walk-ons. Although headliners still had waits that peaked around 45 minutes (e.g., the MK mountains) to 60+ (Soarin'), we got around that with rope drop arrivals and Fastpasses, and never waited more than 20 minutes for anything. I will say that those who don't care to do many attractions and like to spend time in "common areas" and walkways would have found it crowded. Attraction lines were short, so people got in and out faster and spent a greater proportion of their day walking between attractions instead of standing in line for them, so everything always "looked" crowded. Once you saw how short the attraction lines were, however, it was clear that it was a period of lower attendance than usual. (That's why I think a lot of people express shock at how "crowded" the parks are in lower-crowd weeks -- they don't stop to think about all the thousands of people who are NOT invisibly standing in lines! Truth is, except for the first and last couple of hours of the day, walkways are fairly crowded year-round.)
The weather was beautiful, tour groups were scant (and from what we observed as we were running in the opposite direction from them, all from Equador and not badly-behaved!), and only a couple of attractions were down for refurbishment. The only thing we learned about that time of year was to avoid the Food and Wine Festival in the evenings with our small children in tow, as World Showcase was densely crowded with "stumbly" people not looking out for little ones in their path, and fairly poorly lit. (Had we been without the kids, we'd have headed toward World Showcase at that time of day instead of away -- for grown-ups, it seemed a lovely event. I certainly did enjoy hitting up some of the food booths earlier in the day.) I'd visit again in October in a heartbeat.
Always been in Jan and Feb.....first time ever thinking of going in October with just my DH.....wondering which weeks are better in October or Early November for lower crowds/nice weather....I assume late October is busier with Halloween parties etc.....haven't consulted the guides but please tell me your experiences especially in the Magic Kingdom in the Fall! THANKS! 
