I spent weeks looking for a flat seat chair with wheels for my computer work (10 hours a day). All the ergonomic junk actually puts stress in the wrong places and impacts the hips and spine. I went from the ergonomics to the ball chair and that worked okay until the hip stress went the opposite direction. After much research I decided the flat seat would be best. Finding this chair at a great price from Wayfair made it the perfect solution. Pick up an inexpensive seat cushion and you are good to do!  

Pros: Flat seat - perfect for bad hips.
Cons: Two of the holes for the wheels were bent on arrival. With a little work, all is well.