JeffG kindly sent a link to IKEA Hackers: Wide Standing Desk, which reminded me that I haven't updated anyone on my standing desk experiment. What I learned:
1. Wear comfortable lace-up shoes. Otherwise, you may have a problem with your feet swelling.
2. Get a thick rug or mat to stand on.
I liked my improvised standing desk a lot, but I went back to sitting because of a major feet swelling problem—I was too fond of working in flipflops. Also, my improvised stander was an inch or two shorter than ideal. So I may try something like the Ikeahack.
Update: I went back to using a standing desk. I now prefer standing desks to sitting ones, so long as I have a stool available so I can easily switch between sitting and standing.