I went back to WM tonight, but when I tried to swipe for less than $100 like before, I got alternate payment two times. Since a line had formed behind me while I was waiting and the clerk was not one of the friendly, helpful ones, I decided not to try again. I'll go on Saturday and hope for one of the nice ones who might be willing to experiment, but I'm not counting on being successful. I've already started to use the cards for normal spend, since so far I haven't found any other Madison store for MOs that will take GCs.
Fortunately/unfortunately it looks like I'll have a big spend -- just before I got home my car became really loud on acceleration, so I'm looking at some kind of exhaust system repair. It sounds like it's forward, so maybe the whole thing.