[overcoil]

I've used some simple Herman Miller Chairs and all kinds of newer office chairs with contoured seat bottom and seat back curvature - I'm not convinced contemporary ergo is better then any 19th century seat design.
Now I'm using a 80+ year old wooden chair with a flat seat and thin upholstery and a flat seatback. Maybe it's the height and no wheels but I've been very comfortable.

For myself need to be conscious of keeping my back straight when at my desk and not letting my stomach collapse behind my hips. I also think it's nice to switch chairs throughout the day.

I had a nerve injury down my left leg that was irritating me when seated, but just received a new mattress on Tuesday and my leg pain has subsided.