This is a quick update and warning with the experience I have had with my standing desk. Early July I developed heel pain- It sounds from my research on the web that it is plantar fasciitis, but I am not a doctor so I would not make that declaration. Now I also reduced my running from 20 miles to 10 miles a week.
I do not know exactly why this developed, but here is my thinking: I am still overweight so maybe that is a factor. The shoes and boots I am required to wear at work might be a contributing factor. The pain is only when I stand-up or sit up- not when actually standing and it is relieved by walking or running (especially barefoot). For the time being the last week and a half I have been sitting at work again. Actually, last Friday I tried standing for two hours and the heel pain got worse again after subsiding.
More to follow, but I may try re-incorporating standing partially during the day once it heals. Perhaps it was because I went full standing for as long as I could from the get go. I might also try to find office appropriate minimalist shoes.