I think that October is a lot more crowded that the Unoffical Guide claims. Over the last several years, more and more school systems have been going to either year-round school or starting school in early August. Most of these school systems offer a 'Fall Break' either the first or second week of October. It it a given that when kids are not in school, the parks will be crowded.
I do not have enough experience to judge how many people are in a park, or what a really heavy day looks like. When we went to Disney two years ago in early October, the parks seemed very crowded. By 11:00am on several days, it was difficult to move around in the area between Splash Mountain and Big Thunder Railroad (and Big Thunder Railroad was not even opened), and the waits for the major attractions were approaching 90 minutes. However, on other days, the crowds seemed fairly light.
The Unoffical Guide claims that the peak wait time for the first two weeks in October should be about 35-64 minutes, depending on the day of the week. I think they need to do more research.
The parks can handle enormous crowds, if the crowds are expected and Disney isn't in one of its woe-is-me, we-have-to-make-cutbacks moods. I think that Disney as well as the Unoffical guide are being a little slow to acknowledge the growing number of school systems that offer a Fall break, and they are not staffing the parks and extending the hours accordingly. There is nothing more frustrating than to stand in line for nearly an hour only to find that the ride is not loading at full capacity. Oh, I guess there is one thing more frustrating, it is having the park close at 6:00pm on top of that.
But don't take me too seriously; I have pre-vacation jitters. I am going to Orlando the first of October and I just know that the airlines are going to go bankrupt and won't honor any tickets and that they will not be flying anyway due to strikes and I will not able to find any gasoline if I drive and I will get stuck somewhere in the middle of Floridia where there is no electric power due to natural gas shortages and I will get hit by a Hurricane and we will not be able to go outside because of an encephalitis outbreak. And the parks are still crowded! (Which Disney Character am I?)