I've been suffering from severe lower back pain for 30 months, and what appears to be coccydynia for about the last 8 of those 30 months. I have been unable to find any chair that was not painful to sit on (kneeling on a cushion was always less painful). The doctors have been useless - telling me to stop complaining. X-rays and MRI scans showed nothing particularly extraordinary.
I have been working from my bed for the last 2 years, and I decided some 6 months ago that I had to find a chair that I could sit in (I was getting various forms of RSI to add to my problems). I've spent weeks scouring the internet, buying different kinds of cushions, and visiting shops to try out their chairs. Finally, I found this:
Strap chair from John Lewis, UK (no longer available)
I thought it looked ugly in the shop, and that it didn't look functionally different from a normal office chair. I sat on the display model and chatted to the shop staff for 20 minutes, and knew it was going to work for me because I would normally feel the burning sensation in my coccyx within 5 minutes of sitting down.
I received it 2 weeks ago... now I am able to work 8 hour days with only the tiniest hint of discomfort. And best of all, no agony as I try to rise from sitting. I had to wait 2 months for that large department store to get them in stock - apparently they sell out really fast because so many back sufferers find them comfortable.
I hope this information can help someone else.