Thanks for the analysis, and the pointer to Alaska Air (I think I put in for Air Canada miles on my only recent Alaska Air flight, because I hadn't gotten around to setting up an Alaska number).

My feeling is that nonstop to Chicago, Milwaukee, or Minneapolis and then taking the bus is about equivalent to a one-stop flight to Madison, because the bus is a connection (and one the airline won't wait for or make allowances for my missing). That assumes the one-stop flight to Madison doesn't involve a ridiculous connection; when I was looking for New York City to SEA and back it kept coming up with connections in Phoenix.