It's all relative of course-- if one has gone recently in July before (not us), I am sure October still seems empty.
But we are spoiled. It's not just about ride wait times, because we can almost always(see below) handle that with FP, it's about being able to sit on a bench and see sights on the other side of the path every once and a while. It's about finding a table to sit at and eat at Cosmic Ray's... at 2pm. After this last trip, we are now considering January or skipping school in September for the next trip. But we are really, really spoiled.
We don't mind crowds of British people, because they usually go as families, it's the crowds of non-English speaking folks who go in tour groups of 30-80 or so (okay, prob 40-50 max, but seemd like 80

) all following behind the tour leader/ translator holding a flag... ughhh. Five or six groups like this in a park can cause massive waits on non-FP rides or in counter service restaurants. Thank goodness it is usually impossible for such a group to FP.
So January is starting to look good. October now seems to be up and down depending on foreign tour group masses and school fall break correlation (
http://www.disboards.com/showthread.php?t=1065923). But again, we are really spoiled.
The rundown on our trip--
Sat Oct. 7-- MK (yeah I know, Saturday before a Monday holiday is a foolish day for that, it just worked out that way)-- Crowds relative to previous October: extremely high. Heat: higher also. But we always have a plan (and a clue) so, arriving a little late (9:45am) we stayed all day (left around 11pm) and did absolutely everything but Bears, Prezs, Riverboat, Space Mtn., and Dumbo. And we could have done those, but did Buzz twice, Goofy's BSt 5 times, and spent over an hour on TS Island to get away from the flag-following tour groups (FFTGs). Longest waits-- 30 minutes Cosmic Ray's (at 1:30-2pm--midwest Fall breakers'/western-SouthAmericans' lunch?), Speedway 10-15minutes at 10:am, and POTC 15 minutes at 10:30pm or so. Clearly wasn't the ride waits that bothered us a little, it was things like the congestion in certain bottlenecks and the lack of calm sitdown areas (except for the Tomorrowland Back Path, but it was pretty hot there. But we still had an awesome time and no meltdowns even though we were there over 12 hours ... the TS Island break helped
Tip/learnin' of the day: TS Island and PeopleMover can be relaxing places to prevent meltdowns on hot crowded days .
Sun Oct. 8 -- DMGM -- Crowds relative to previous October: same. Heat: higher. Other than the usual nightmare for those silly enough not to FP RNRC (even our fp wait was 15-20 minutes, which is looong for our spoiled selves) and the bottlenecks of the LightsMotors show, there was never a time we felt really crowded at DMGM. Didn't notice any FFTGs (flag-following tour groups).
Tip/learnin' of the day: as everyone here already knows, RNRC is FP mandatory. And Pizza Planet is still lamely themed.
Mon Oct. 9 -- ride the monorail circuit to explore resorts, boat to Ft. Wilderness, etc. No crowds in these places, of course.
Tuesday Oct. 10 -- Epcot --Crowds relative to previous October: same early, higher later. Heat: higher. Went straight to Soarin' to get FPs instead of TTr. LivingLand line looong, no FP, skipped. Crush line huge by 10:30, we skip til later. Had a fun day, with crowds not coming into play except at lunch (FFTG went into Electric Umbrella just as we were headed there, so no EU for lunch). McDs fries for lunch, mooching ducks for entertainment. First meltdown of trip (d*** those Thomas toys in UK section-- crack to our spoiled Thomas addict). Fun day continued after settling. Lines at food/wine booths not long in mid afternoon. Kidcot/International-kidcot stops not crowded. TTr FP return time several hours (got ours around 11am for 3 or 4pm, if I'm remembering). Mission space walk-on. Just as we are walking by Nemo entrance they open for testrun. Ride stops when we are 90% through. They walk us out 10 minutes later. Crush line minimal (one show wait), so we hit it. SpaceEarth (best thing there IMO, they should have headsets to translate narration into other languages for non-English-speaking folks) as leaving.
Tip/learnin' of the day: if you decide not to rush to do Crush at first show (10am?), best other time is late in the day.
Wedn Oct. 11 -- AK --Crowds relative to previous October: same early, higher mid afternoon, (around EE, as always probably), nigh empty EMH. Heat: lower (cloudy). Got EE FP, hit Safari, see Africa animals, hit Kali, etc. Easy FP on everything available. EMH at AK , aka Soaking Wet Kids Hours ( rode Kali again, saw a kid who had stayed on 4-5 times

), not crowded AT ALL, 3 hours of awesomeness.
Tip/learnin' of the day: this is the late EMH to hit.
We will probably go again in October, but are so spoiled that the MK day did scare us a little.