I've been looking at one for a while, but haven't made the purchase yet. The shop where I bought my machines, and take them for cleaning, sells these chairs and they are (sorry) Heavenly! I've had many types of office chairs over the years (as I work in an office) and not one comes close to how these feel.
If I'm in that chair for a couple of hours a day, that's more time than I spend in any one place else (except work). Also, I look at it as a long-term investment - not as something that would have to be replaced every couple of years.