At the web design firm I work at, Ply Interactive, we have Aeron chairs all around. I sit on those and I never experience back pain.

But when I get home, the chair I have is an el-cheapo chair that is hard to sit on and wears away at my lower back very quickly.

The Aeron chairs are expensive as hell, but considering how long I sit on chairs during business hours, maybe it's worth the investment.