So you aren't crazy about the Aeron, or you don't want to follow the crowd. Maybe you don't want to pop for the big price tag. (At BetterSource, we sell the Aeron for about $550 used. They go for about $900 new.) What are other chairs should be considered?
The Herman Miller Embody chair (Photo at right from Herman Miller Seating.) is their latest attempt to follow up the success of the Aeron. It has a spine-like support system and is a very complicated chair to operate. It was co-designed by Bill Stumpf who designed the Aeron with Bill Chadwick. I have sat in this chair and found it very comfortable. But I have heard differing reviews, particularly that smaller people don't like it as well. Herman Miller Seating sells the chair for $1495. Knowing Herman Miller, a dealer that advertises the chair has to do so at that price. But you can probably buy them for considerably less if you call, particularly if you buy larger quantities. 
The Humanscale Freedom chair (Photo on left from Humanscale site.) is probably the most successful premium priced chair (Above $500) that is a good alternative to the Aeron. Mark Erickson of Mark Erickson Associates, who used to work for a Herman Miller dealer and has sold thousands of Aerons prefers the Freedom. "When I sit in the chair, it seems to follow my body." Said Erickson. Indeed that is what Neils Diffrient intended when he designed it. It is one of the simplest and most easy to use chairs. New Freedom chairs sell for about the same as the Aeron. Used ones for under $350. The Steelcase Leap chair is hugely successful in terms of volume shipped. The Humanscale may not outsell the Steelcase Leap, but then again, Steelcase discounts the Leap to get the large national contracts and sells the chairs as part of packages with cubes and desks. The Leap, which has no mesh, is one to consider as an alternative.
The Contessa chair, from Teknion, is less well known, but one of the few chairs to feature a mesh seat as well as back. This chair is one of my favorites. It has a seat sliding adjustment to accommodate longer or shorter legs, which the Aeron does not. Its controls are on the arm pads, so you don't have to reach under the chair to adjust. It is a very good-looking chair too. It is premium priced comparable to the Aeron. They are hard to find used, but will sell for less than a used Aeron. (Photo of Contessa below from Teknion Website.)
The Knoll Chadwick (Photo below right from Knoll website.) chair also has a mesh seat. I like this chair and as the name implies, it was designed by the designer of the Aeron. It can be purchased new for less than the Aeron, usually less than $650. One doesn't run across very many used ones.
Some others high-end chairs of note are the Allsteel 19 chair, the Knoll Life Chair and the Haworth X99 chair.Going lower down the price scale are a group of chairs that tend to have fabric seats and mesh backs. My favorite is the Office Master Yes chair (Photo at below left from Office Master site.) that can be purchased new for $350, considerably less than a used Aeron. The chair has adjustable arms, a memory foam seat and choice of seat colors in Teknit fabric. It is a great value.
At the bottom of the price scale are the knock-offs from Asia. These come in various names and many can be purchased for at or below $200. There are some that were copied directly from the Yes chair. Of course there are many others, but these are a good starting point. Talk to your favorite furniture dealer for more alternatives.
SRK
