Rented again from Silvercar at ORD. Pickup is now from the Bus/Shuttle Center, which might be a decent walk from your terminal. When I mentioned this to the pickup driver, he said they could pick up from the terminal, if you requested. So, you might want to do that. Location is in the same place, about a 10 minute drive from ORD, so roughly the same distance/time as the Hertz/Avis/National lots.
Also, FYI, our pickup was in an A4, so if you've got five people in your group, you should let them know when you request pickup, otherwise you're not all going to fit into the car (since there's room for four plus the Silvercar rep).
Car was a 2016 A4, about 28k miles, looks and drives like new. The rep said they had four or five 2017s in the fleet, and would be getting more, but that they're "bottom of the list," with SFO, LAX, DEN, AUS, and MIA being the locations that get the new cars first. He also mentioned that vehicles get taken out of the fleet once they hit 35k miles.