I did it once. Worth doing! I was coding at someone else's house and they had a standing desk and sitting desk. I was at the standing desk all day, partly out of necessity and partly out of curiosity.

By the end of the day, my feet were a little sore and I was a little more tired than otherwise, but I felt more active while I was doing it. I would like to try it again before committing to a new desk, however. Now that I've been reminded of it, I'm already thinking of how I can try that at my place.