DJBens77 saidI do and I love it! There was a thread about this a while back!
Hey! Just for the record there was even _earlier_ post about this
Basically, it sounds like a gym ball is a good long term office chair solution, for the majority of people anyway.
I used the ball for awhile as an office chair and it felt great, cool, and hip! And then we had office environment inspections and this bitch of a woman comes by and very coolly seems to say "I'm not going to be your mom, but I'd recommend you not use the ball because of (bobloblawloblaw) ... in the end, though." I then get a forwarded email from my supervisor where she writes "I tried to tell him that the ball is bad, but he blatantly ignored my words." Ooooh, was I pissed.
In the end though, after posting that above thread, I felt everything turned out for the better (my supervisor told me to get rid of the ball). It seems to make sense that a ball is not meant to support your spine ergonomically and that putting constant stress on it for 8 hours everyday was not a good idea (of course it's still great for workout).