I gave up on United some years back, after a delayed flight from Orlando arrived in Chicago at the next gate to my London flight, which was still on the ground as we landed (and had a number of connecting flights coming in). In the short time it took me to get off the plane and the few short yards to the gate I was told my flight had left and I would have to wait for the next flight late the following day. I had to wait (literally) hours to get to my contact lens stuff from my checked bags and then make my own way to and from the very down-at-heel hotel they had recommended, which was not in a salubrious part of town.
No food or drink given, no allowances made for the fact that I was at that time quite high on their frequent flyer program, no allowances made for being a lone female, and when I complained (once I'd reached home, having lost out on some paid work into the bargain) I was told it was just one of those things. No apology, no compensation. All because of the weather. And yet, of course, it wasn't. A ten minute extra wait at the gate for the London flight would have enabled most of the connecting passengers to have made the connection.

So for me almost any airline except United from here on in.