I posted in the Nov 1-15 open thread about my initial experiences with a standing desk (initially improvised, then I bought a proper one) to replace my old crappy desk. I try to alternate between standing and sitting when I get tired, and I plan to get a stool for the same reasons you stated. Even at work where I sit all day, I get up and walk semi-regularly (I'd estimate every 60-90 minutes) if only to refill my water or use the bathroom.