With the kiosks now in place, I think a roughly 2 hour connection is plenty of time to connect at ORD. That's not something I would have said a few years ago.

Those who have never made a connection from 1/2/3 to 5 (or vice versa) at O'Hare, and who aren't residents parking cars, have probably never used the train and have no reason to be aware it exists, since it's pre-security. Terminals 1, 2, and 3 have land connectors airside, so anybody connecting between those terminals just stays airside and walks. If you happen to find yourself outside security on the departures level, look outside across the drop off area, and you'll see the train one story above.