I second schmutzig's recommendations. Even at a busy time, the lines at MSP move well. If the gate is usually 21 (that would be the c or g concourse) you will need a 10 minute walk, and maybe at most 30 minutes to get through security. Check in is a breeze. I don't believe I have ever waited more than 20 minutes for tsa, and it is usually closer to 10 minutes.

Things move smoothly at MSP. My wife likes to get there two hours early,and we end up just sitting around for a long time. I use it to go to the observation deck, and I am not so bored.