I switched to a standing desk 3 months ago. It has been a great thing for me.
My thoughts to those who want to try it:
+ Give it time. The first 3 days were hard. After a week, it started to feel normal.
+ Get some padding. I'm using a cheap Yoga mat. I've heard gel mats are ideal.
+ Suck in that gut. If you practice keeping your lower stomach muscles tight when you start. This will help your back muscles learn to be straight.
+ Put both feet on the ground. Leaning on one leg isn't good.
+ Move around. Sway from side to side. Pick your feet up regularly. This helps keep your body and legs healthy.