I definitely agree with the last post. If you have enough room, I would consider another chair, that is lower at it's lowest point and on a larger base.
I have a Callisto, and also a much cheaper ABCO chair and would probably go with the ABCO over the Callisto.
I also have to add, I have had no mechanical issues with either.
Have a look at the chair that Algeos have, it seems really good for the money. Also the DBS one looks good too, but is similar price point to Callisto.