A good dose of common sense regarding standing desks is in order. Basically you're trading one set of hazards for another.
"Individuals spending most of the day on their feet every working day are at greater risk of health problems including varicose veins, poor circulation and swelling in the feet and legs, foot problems, joint damage, heart and circulatory problems and pregnancy difficulties."
"Chronic heart and circulatory disorders are linked to prolonged standing at work. Prolonged time in an upright posture at work may cause hypertension comparable to 20 years of aging."