Having been born and raised in the Madison area for 20 years, and moving to the TC, and living here for 3, I can tell you that the differences aren't THAT substantial, apart from the obvious (size, traffic, etc)..
One thing I will comment about Madisonians, is that they are VERY, VERY, VERRRRRRYY proud of their city. It always seemed to me to be the liberal mecca of the midwest... Very very forward about politics, and people are extremely concerned about keeping their city clean and quaint, yet with the amenities that you wouldn't find in other cities of its size. That being said, its a great place to live, and I love going there to visit old friends, and my parents.
Reasons I moved? Aside from need of a change of scenery (and getting at least arms length distance away from my parents), the "Dane County Psycho Liberals" (as my friends and I liked to call them), really got obnoxious at times. Its a very political city, and any viewpoint that hints SLIGHTLY to the right, typically is shunned upon. Wasn't a fan of that.
I also notice many people are commenting on its close proximity to Chicago. I greatly enjoyed this as well when I lived there, however, now that I live in the cities, I notice something- I'm not as enthused when I go to visit Chicago. Just about all of the shopping and activities (with exception to nightclubs, and the spectacular museums Chicago has to offer), is all available here in the cities... Plus, you don't have to pay tolls to get there

!
As far as people go... seems the same to me. When I moved here, I fit right in. People probably thought I was MN born and raised. Truly two very very comparable areas.