I use this chair for about 4 hours at a time and find it to be the most comfortable I've owned. The lumbar and tilt adjustments allow me to find the most comfortable position.
I got it for only 100 USD and its a great chair. Thanks to the mesh the seat is more flexible than other chairs and its actually very comfy and yet provides good/firm support. Lumbar support is a bit flimsy but does the trick. Also the arm rests are flimsy plastic but in the lowest setting they are sturdy and provide sufficient support. Mesh also keeps the chair cool and ventilated - overall great chair for the price. I bought another one for home use.