I don't disagree with any of your points. However, I did the second week after opening and decided I don't want to do it again.
1. The heat and (mainly) humidity is still awful. While it's not a guarantee that it'll get better in October, the chances are better. This reasoning really isn't for me personally since I'll deal with whatever and have a good time, but my trip was negatively affected because the "non theme park" people in my group were miserable the entire time.
2. This is actually the main reason for me not to go second week. Being from out of state and not planning a second visit, it felt like it was too early to go. Going in October, you get to build the hype by seeing the posts of people who have already gone and reading all their reactions. Going the week after open, while it was fun when I was there, it really sucked knowing that it was going on for so long after my trip and wishing I could go again. Every post and Tweet I saw just made me disappointed that I wasn't experiencing it. It's a silly reason, but it will be a significant contributing factor when I plan future visits.
Again, I don't disagree with anything you said because you are spot on with every point you made. It was my first year going that early and I decided it wasn't for me.