Well, I finally settled on a new chair. I got the Office Depot branded mesh chair.
It is working out very well -- not quite what some of the big $$$ chairs are, but so far so good. I can sit it for 6+ hours and not die, which is a huge improvement over what I had going before.
http://www.officedepot.com/ddSKU.do?...%206&An=browse
I coulldn't see much difference between this chair and the more expensive Ergo-Human line other than the tags and price...