We have a few Life chairs at the hospital I work at. I wasn't too impressed - much happier with my Aeron at home and Knoll Bulldog at my own desk (sadly, discontinued). We also have a ton of Knoll Chadwick chairs, and they are terrible - remarkably uncomfortable and they started falling apart just a few months after they were acquired. At the moment you'd be hard pressed to find more than a few in the entire institution where at least one armrest hasn't broken off. YMMV of course.

I've spent the last year with one of these at work. Though I haven't tried any of the others mentioned here, I absolutely hate this thing. Not only does it break easily, but it quickly becomes uncomfortable, and have had incredible back pains because of it.