There are two reasons why I put very very little stock in negative reviews of Disney resort buses:
1) People very rarely post positive reviews when normal things work normally. For example, you almost never read reviews saying, "I checked into my room and there was no trash on the floor" or "No rides broke down while we were there." So it's not like negative experiences with AoA buses are so common, it's just that no one bothers to write positive reviews, so it seems like the negatives outweigh the positives even though that's not the case. Buses at every Disney resorts are supposed to run about every 20 minutes. If that occasionally happens less often it's not a function of the resort itself, it's just bad luck. Which brings me to ...
2) Any system, any system at all, can have temporary glitches. Unless someone is there many weeks at a time comparing all different resorts over many repetitive trials, they aren't seeing a true representation of what really happens. i'll give an example from one of my own experiences. The one time we stayed at the Polynesian, we had amazing luck with the timing of buses. It was uncanny. During our entire week there, we literally never waited more than two or three minutes for a bus at the resort bus stop. After a few days we started joking about it but it continued to be true. You'd think I'd have come back writing reviews about how incredibly wonderful the bus system was a Polynesian. But I know that's not the case. As we joked about how lucky we were, we joked that there might be some unlucky family following our exact same schedule all week but just five minutes behind us. Those poor folks would've waited about 20 minutes for every bus during their entire stay, and they'd go home to write a review about how bad the Poly bus system was because they always had a long wait. See what I mean?
So in short, don't let bad reviews stop you from taking the bus. That being said, the bus system isn't for everyone, regardless of whether it's a busy season or not. Some people just can't stand not being in control, and most of those people simply are not going to enjoy taking the bus all week, they'll likely feel quite frustrated at times and would probably be better off driving themselves. In the real world, I'm one of those people. But when I'm on a Disney vacation, I happily turn off that part of my brain and I'm thrilled to let other people take control of some of the things, such as getting there and back.
Whatever you do, you have a great plan for going during that week of the year, which is getting to the parks very early. I'm sure you'll have a great time no matter what you decide.