I love that this thread is still alive
..and thanks for all the suggestions, particularly ERIS and Old Irving, which I'm not sure how I didn't know about--they're close enough to ORD to be possible even on a shorter layover. (I was actually at ORD 3 weeks ago, but an op-up on the inbound meant that I spent my layover/weather-related stranding drinking free beer in the Polaris lounge before giving up and getting a hotel)
I'm not sure when it'll be, but the "brew district" is going to be my next layover destination.
I hope I've inspired some other people to enjoy long layovers too.
Allow me to partially hijack my own thread: any Chicago breweries make good kombucha? Next Chicago trip I may have company; Mrs. Säufer, somewhat ironically, doesn't drink.