Mark Lukach posted the ultimate research summary on stand-up desks on Wirecutter:
… The standing desk fad that you keep hearing about is based on a pretty substantial amount of research. Dr. James Levine of the Mayo Clinic has a scary statistic to share: here in the US, we spend more than half of our waking hours sitting down, split between watching TV, driving a car, and working at a desk. This is not good. …
… Ernest Hemingway stood while he worked. So did Thomas Jefferson, Leonardo DaVinci, Benjamin Franklin and Valdimir Nabokov.
On the contrary, Winston Churchill once said, “Why stand when you can sit, and why sit when you can lay down?” However, it turns out that Churchill was not being completely honest when he said this–Churchill stood when he worked, too. And he lived until 90. …
Best Standing Desks

I’ve had no luck at all trying to sit on an exercise ball. Standing, for a time, works for me.
(via Kottke)