Everyone seems to use a standing desk to stand, I use a standing desk to walk. Standing still will definitely murder my back, while walking feels comfortable and natural. Long term effects might be bad, but sitting down just feels uncomfortable after a while, even on very good ergonomic chairs.
I don't actually walk, since a treadmill takes up too much space, but I do shallow side squats and similar exercises while working. I'm a bit hyperactive and found this helps me stay focused better. What you need to do to type easily while doing this is have your desk so that it supports your forearms solidly so your body's movement (and there always is some movement of your shoulders and upper arms when you move your legs) is not transmitted to your hands. I am not an especially fast typist though and someone who is may have a bit more trouble, or may be slowed somewhat.
I've been wondering about something similar myself - do you walk the entire time you're working? If so, do you use a combination of a standing desk and a treadmill, or something similar? Do you find it tiring to do for 7-8 hours, and does it give you any other problems, e.g. with your feet?
Yes I walk the entire time and I don't find it tiring; I do tread lightly and walk on bear feet. I don't use a treadmill either; I walk in-place which is much (for me) less tiring than a treadmill which takes starting up and ending. In place walking (even on a WII board which counts what i'm doing) is very comfortable IMHO.
