I spent March through June this year working on a project in Milwaukee and flew in and out of ORD every week. I would land in ORD at 12:00, get my luggage and rental car and would be in downtown Milwaukee by 2:00 -- maybe 2:15-2:30 if I stopped to get something to eat. The actual drive from ORD to downtown Milwaukee was less than 90 minutes.

Depending upon what time you will be leaving, the drive back to ORD can be quite problematic. I always took the last flight home on Thursday night, so I had to leave Milwaukee around 3:30 or so for what was inevitably a 2 or sometimes even 3-hour drive, depending on the traffic.

I decided to drive and forego the extra miles because I could get to the Milwaukee office quicker by driving from ORD rather than connecting on a flight to MKE, and for the flight home, I wasn't willing to risk missing the last flight home on Thursday night because of some problem with the MKE-ORD segment. There were at least three or four weeks where I would not have made it home on Thursday night due to delays and cancellations had I flown MKE-ORD-SMF. By just flying ORD-SMF, I was delayed, but at least I got home that night.

In my opinion the potential hassles of UX delays and/or cancellations out of ORD is not worth the extra 1000 miles (plus bonuses) each trip. Of course, if you need the miles to get or maintain some status level, then it may be worth it. YMMV.