At home, I've been standing or walking on a treadmill for about a year. I find walking actually easier on the feet. My current 'desk' is a prototype of 2×4s and plywood, which I plan to replace with something nicer (with a matched 'skin' for the treadmill) soon, now that I've settled on positions for monitor and keyboard. The treadmill (purchased used) has the upper section removed so as not to interfere with the desk and keyboard, and the controls set off to one side.