We have three, although the last was purchased in a work stool height, and is missing the mechanism that would allow it to tilt forward and back, where our desk chairs do have it the tilting feature. I thought about trying to get it changed, as it really makes the chair more comfortable, especially in a higher chair where your feet aren't touching the floor. I bought it on a whim to sit at my computer around the dogs, where my computer is at counter height 36 inches. All my brain cells weren't firing at that moment I made the purchase impulse at a sale, and I didn't make sure it had the tilting mechanism. I just never thought about it not being included on all models.
The Aeron seating manufacturer is Herman Miller, a long time giant in the development and study of the working environment. It is really great to see them everywhere and all over TV, including news shows and American Idol. I have to say it is so nice to see the general public and businesses going for a good design instead of just any office chair to sit on. I am hopeful it will make design more important in the United States. One of the best things about this chair is the fabric and the fact that it breathes. The summers get very hot and humid in the Washington, DC metro area and I haven't been able to convince myself that switching to a newer ergonomic design upholstered chair would be as comfortable.
The designers of the Aeron Seating are the late Bill Stumpf and Don Chadwick. I can remember as a young designer attending a lecture by Bill Stumpf about the Ergon chair he had previously developed for Herman Miller. It was one of the first ergonomic chairs on the market. New chairs have been developed since the release of the Aeron chair, with advanced ergonomic features and new design looks; but for me it has an upholstered seat and upholstery can get dirty in a shop environment.
After about 9 years we had a problem with the seat in the Aeron desk chairs. Herman Miller knew that they had a problem with the construction of the seat and replaced them. They stood fully behind their product. I think this is noteworthy in today's world. With a little clean up my Aeron chairs, which receive heavy use, look like new. I highly recommend this chair for total comfort in a work chair. Check out the Aeron chairs at: http://www.hermanmiller.com/Products/Aeron-Chairs