They are extremely comfortable. I had one job long ago where they gave me a tiny ugly pink secretary chair with arms that were breaking.
The backrest was PERFECTLY set at my lower back and I could sit at it for hours and hours with no discomfort at all.
They replaced it with one of those mesh monstrosities and I had a fit; I did not want a HAMMOCK – I wanted to be ergonomic.
So, I got my ugly chair back and I was happy.