Having tried standing, I can tell you that I found it to be rather uncomfortable and unsettling. Standing upright is, in my opinion, a transition state. That is

Having tried standing, I can tell you that I found it to be rather uncomfortable and unsettling. Standing upright is, in my opinion, a transition state. That is, you normally only stand upright in between walking and/or sitting. So, when I'm standing at a desk, I desperately want to be moving to the next state. Physically, this works out okay for mousing tasks, since those are one handed and offer a large degree of freedom. However, it just doesn't work for two handed tasks, like programming or writing, which anchor both of your arms, because your arms are critical for balance and, thus, movement. I also found that this desperation to move around while standing affected me mentally. That is, when standing, I was fine doing short, low-attention tasks like responding to email or IM, since I coud move a little between each task. However, for longer tasks (again, like programming or writing) I found this to be maddening. I felt as if I was constantly being tugged and distracted by this urge to move.