Good lord, you can stand the single lane from Mt Vernon to DeWitt? And then again from Clinton to Morrison? I will take that route if I'm anywhere east of Calamus but otherwise I always drop down to I-80.
Anyway I've probably driven Chicago to Iowa and back again at the end of the week roughly 120 times (I wish I was exaggerating) in the last 2-3 years. Granted I have the I-Pass, but you cannot beat 88 for time and ease of drive. Once you hit the tollway (roughly mile 44 or so) you can go however the hell fast you want. That first 40 miles is heavily speed trapped so watch out. The I-80 to I-55 route will add at least 30-45 minutes onto your drive, so really you'll come out close to even on the tolls when you factor in gas that you're wasting by taking the long route. I-80 does have more places to stop and eat though. I-88 basically has Silvis (a subway), Rock Falls (Culvers, BK, Hardees) and then the worst oasis in the illinois tollway system at Dekalb (Subway, McDonalds and Panda Express). I would highly recommend 88, especially if you're not used to a longer drive.