It's actually amazingly comfortable. Moreover, balancing requires you to sit erect, helping fight the second scourge of computer dorks -- bad posture. (The first being Carpal tunnel.)
That's interesting. I might buy one just to try it out then, I hurt my lower back a couple of years ago and it never fully healed, and slouching on a leather chair all day doesn't seem to be helping..
(thanks for the inspiration)
Let me know how it works out. I did it initially for similar reasons. A surgery I had years ago leads disk degeneration. Mine is not bad, but my back did hurt at the end of the day sometimes. Now it does not.