The only thing I would add to that is that although some positions and such seem comfortable, they still do alot of damage. I've also got no problems with wrist, stiffness of the hand or even neck despite what research shows vs; my actual use.

And oddly enough, my chair is totally "ergonomic", created by a reputable computer-worker oriented company and is very comfortable. Despite all that, sitting in it too long is exactly what "happened" to my spine. It's entirely possible that a cheapie stiff chair with no ergonomic styling may have saved me from three surgeries!

Since it seems impossible to know just what is going to affect you or how, make sure you stretch and do excersizes to maintain good back health daily. I'll post something shortly (have to scan paper) on some simple and easy excersizes you can do that my physical therapist recommends.