The Wall Street Journal on a Texas A&M study on standing desks and their impact on productivity:
The researchers attributed much of the productivity gains to the greater physical comfort reported by the workers at the higher desks. Nearly three-quarters of those workers said that they felt less discomfort after using the desks for the six-month study. The greater comfort was consistent with prior research showing that standing desks offer benefits to their users—by helping them burn more calories, for example, or improving their concentration and other mental powers.
Yep. But remember, you have to stick with it through the initial discomfort.