Business Week has an article about the latest research that shows that sitting in a chair (any chair) for hours each day is harmful to your health.
Excerpts from Business Week’s "Your Office Chair is Killing You":
Hamilton, like many sitting researchers, doesn’t own an office chair… The data back him up. Older people who move around have half the mortality rate of their peers… The best sitting alternative is perching—a half-standing position at barstool height that keeps weight on the legs and leaves the S-curve intact. Chair alternatives include the Swopper, a hybrid stool seat and the funky, high HAG Capisco chair. Standing desks and chaise lounges are good options. Ball chairs, which bounce your spine into a C-shape, are not.
Nate Rosenberg 
Do you have personal experience with one or more of these chairs. The concept is logical. They are quite proud of their chairs I can see. If I spend a lot of time at a desk, I would have to consider jumping on one of these.
I haven’t tried one yet but would like to.
I’ve been working from a standing desk for about 17 months. I don’t track any metrics to measure this, but I feel more productive and I am more inclined to go to the office rather than work from my chair at home.
If I am sitting through a meeting I restless quickly which is a positive outcome from my perspective because I feel I am not likely to suffer quietly wasting any time.
we have different office chairs in the office and i love to use those office chairs with clothe cover ~`;