Used to have one at an old job but never liked them. I found the plastic leading-edge of the seat gouged into my legs uncomfortably. I did find one with a torn mesh seat on the street once -- repaired it and gave it to a family member.

For me - I've been sitting on a Humanscale Freedom for about a decade. The company replaced the gel seat once due to wear and tear - but otherwise it's been a great seat if you're okay using something that doesn't have a million knobs and levers to customize your sitting experience.