IMWP's son here. My wife and I chose Mizzou for grad school basically because, between having tuition waived and paid GRA positions, it cost next to nothing (Dave Ramsey probably got randomly horny the moment we made that decision). We never even visited Columbia, but, I must say, we really enjoyed our two years there. It's on the northern end of the beautiful part of Missouri, riddled with hike and bike trails, and the people there were good to us. Plus, Columbia is a very affordable place to live. For example, we were not flush with cash, but had plenty of good restaurant options for dates and meeting up with friends.
As for the university, I think I can explain the perspective of Mizzou fans being over confident. Mizzou is the only major DI school in the state and our nation's oldest university west of the Mississippi. It's like Nebraska in that many Missourians never consider another school for undergrad. This cultural status gives Mizzou an undeserved local mystique. Most students and alumni don't care too much that they are solidly mediocre at sports, but support the team and attend games as per tradition. As you'd expect the social tailgating scene has more energy than the games. I guess you can say early football success in the eastern division was a nice boost of confidence, but, otherwise, only cocky, ignorant undergrads are going to talk much shit.
Personally, I never became a huge fan of their athletics. They were not good at anything when I was there, and the SEC chest thumping was nothing compared to aggy but still annoying. I've held on to two shirts and always hope they can upset higher status SEC opponents. That's about it.
TLDNR version - I went to grad school at Mizzou. It is Nebraska's better looking cousin who has a better personality but doesn't have a glory days to fall back on and hates it's neighbor Kansas for having one elite sport.