I had something similar to the OP after Thanksgiving, but on AA. Weather at ORD meant lots of delays. I was coming from MSN, and missed the first standby connection I had wanted. So, there was another (that I probably wouldn't have cleared on), my original flight, and a flight to PVD, that was scheduled to leave about 45 min before my ticketed flight. Well, I found out I wouldn't make the earlier BOS flight, and my upgrade would almost definitely not clear on my flight, so I asked about PVD. The agent got me on the flight, got me a seat in F, "forgot" to charge me two stickers, and then I found out that even with the hour drive in the rental car, I still beat myself home. And, the cost was a wash. Cab: $35 to my house, plus the $60 for stickers (I had none, would have had to purchase then and there), and a snack at ORD (as I would have been in Y to BOS) made the hundred bucks seem not that bad for the car. I found out that my BOS flight actually left 1.5hrs after the PVD flight. So, sometimes it really does work out for the best.