I fly United/Ted out of O'Hare all the time, and have had very little trouble. Security is quick, so even a long line only takes 5 or 10 minutes of waiting (usually). UA has self check-in kiosks or if you have luggage you can also use the Skycap (curbside check-in).
United has the sole use of Terminal 1, and the terminal has two concourses, B and C. When you clear security, you're in B. If your gate is in C (Your gate is C19, for example. If it's B19 then you just stay in the B concourse) then you need to get to C by going down to the long hallway underneath the tarmac (follow the signs that say "this way to C Concourse"). The hallway is kind of cool, really. The have a really neat-o neon light sculpture (for lack of a better word). It's a bit of a hike, so make sure you give yourself plenty of time. And if you or someone with you has a hard time walking, you can ask for wheelchair assistance.
Once at the gate, United/Ted is very organized. There are several fast food places to get somthing to eat in both concourses, and some smaller stores and newstands. They also have small Chili's restaurants if you want more of a sit down meal. And Starbucks! By the way, United/Ted dosen't serve meals anymore on flights under 3 hours, so if you think you want to eat something, you'll need to bring it along yourself. Ted does sometimes sells sandwiches and salads on board (they're pretty good, really) but not from O'Hare to Orlando, the flight is too short.
Gernerally, United/Ted is as about on-time as any other carrier. My largest delay was about an hour for a mechanical problem. They switched aircraft, and even managed to have the new aircraft go to the gate next to our orriginal plane.
Ted is all one class seating, and Ted has the route to Orlando. If you fly to another city on United, they do still have first class, but the odds of getting an upgrade are zero. Even big time frequent flyers can't always get them, a general member has no chance what so ever.
I've always liked United and have never had a major issue with them. Other's have had problems. Its really all luck, I guess!
Have a great trip!