Three days ago I stole it. No - not to secretly dispose of it, but to sit on it when I am at the computer!
It has already done wonders for my middle. I suddenly feel toned and have a spring in my step. I tried everything else - from chairs to couches, to barstools, to standing, to walking on an exercise machine - while writing, but nothing made any difference, or was too annoying. My time at the computer has expanded to such a degree that the "how" of it has become important. I have been looking for a way to make it more positive for my health.
Sitting on an exercise ball is not new - and not to be recommended if you are doing delicate design work - but for writers, bloggers, researchers etc...it turns all that unhealthy "blob" time into exercise, which reduces your middle - and your guilt for all the time you actually don't HAVE to spend on the computer, but do so anyway. I am now wiggling on my "chair" like a little kid all the time, and I sometimes even get close to falling off, since I do role, bounce, and balance on my ball when I am waiting for uploads.
I am thinking of sending a whole truck load of yoga balls to my daughter's office.
PS: "My" stolen ball is a 65" version. When I put my lap top on the pull-out keyboard tray of my desk, it works out beautifully. Even sitting still, it has me sitting in a much better posture than I used to, in just my regular chair.
These balls also come as chairs in many design versions- which is very clever for the office, but I think you would role around less and only get the posture advantage.