Sorry to reply to myself, but I keep forgetting to bring this up.

I think it would help those of us trying to predict whether to "gamble" on a complementary upgrade (vs. paying cash or credits) if our posts to this thread would include whether or not Biz class was full on their flight. If I find out from this thread that MKE-LGA often has empty seats in Biz class, I will be more tempted to hope for a complementary upgrade. OTOH, the reports here that MKE-LAS never have free upgrades tells me to plan to pay for biz class on that route.

Does this make sense? If not, don't be afraid to say so!