I evaluated this chair, HM Mirra, both the original and version 2 models of the Steelcase Leap, and Humanscale Liberty and Freedom chairs, and ended up with a used original Steelcase Leap high-back.
The Aeron is a good design in my view. But when you're picking out a chair bear in mind the following:
1. Aeron is based on the principle of a rocking chair. The back does recline slightly as you rock back (that is to say, the angle between back and seat increases as you rock back) and that's ergonomically sound as far as sitting in the chair is concerned, but for a desktop computer user it will lower you quite a bit relative to the screen especially since the pivot is close to the front of the seat. The good news is that back support stays very consistent because the back and the seat keep touching each other through the movement. The other models are basically recliners; the seat pan slides slightly forward but does not go down, while the back lowers, so you stay more level with the computer. Downside is that lower back support on recliners weakens as you recline because the pan and back separate a bit. You will in my view retain slightly better posture in a reclined position in the Aeron than you will reclined in other chairs.
2. Particularly concerned about lower back support? Aeron's PostureFit and their standard lumbar are both better than the competition in my view. PostureFit is good for an upright sitter but a bit uncomfortable though when reclining. The standard lumbar is uncomfortable set in its standard position; lower it all the way and it is does what I feel it should do.
3. Because of the mesh, Aeron is not particularly well shaped around the upper back. Next to the Humanscale Freedom or Mirra, upper back support is questionable; next to the Leap or Liberty, Aeron's upper back support feels almost non-existent. Humanscale's Liberty, also a mesh chair, solves this problem by creating a curve similar to the Leap by way of sewing three panels of mesh together side-by-side in vertical strips, much in the way a nice pair of bike shorts or tights would work, instead of using a single panel that can't really be properly tailored.
4. Sizing is really important. In my view, the Aeron's adjustability does not allow for enough different body types and also Aeron sizing runs "small"; size C kicks in for most people above average height. Also on the Aeron, you cannot adjust seat pan depth, while you can on the other models. So you have to have it right to start with. Someone with short legs and a long torso is going to be in particularly deep trouble on the Aeron, as you have to go with the deep-seated C size in order to get a reasonably high back. Aeron's B size has a back that in my view is much too short given the size of the chair. And you cannot adjust the arms on the Aeron laterally; you can pivot them but you can't actually slide them into a narrower setting as you can on the Leap. Another reason to make sure you're getting the correct size. (HM fixed this particular issue on the Mirra; let's hope they issue an update for Aeron).
5. Mesh selection is also really important. There are a number of new fabric options on Aeron which are much firmer and frankly in my view more comfortable than the original pellicle. Also, I wonder about how durable the pellicle is; it seems to me to be rather like asking for trouble. If the pellicle feels too much like lawn furniture or dumps you into the mechanism underneath the seat pan, you might want to consider the denser, tweedier looking fabrics such as "wave."
As I say I ended up with a used high-back Leap. The Humanscale Freedom is meant for a very small person; the Liberty's arms are even less adjustable than Aeron; I was concerned about the durability of the Mirra's plastic back, even though it is ergonomically excellent, and the Mirra's seat pan is quite small; and the new Leap is slightly smaller than the old Leap high-back (though much better than the old Leap standard back) and has cheap and nasty padding on the arms, thinner padding on the back and not as good a support in the lower back, although to be fair it also has substantially nicer padding on the seat pan than the original. Overall I would say that either the new or used Leap is capable of fitting the widest range of people in a single chair. Humanscale Liberty is an outstanding choice if you don't mind the rather wide fixed spacing of the arms.
Overall, getting a "commercial quality" chair is worth it. Compared to Office Depot and Staples self-assembly, the chairs from HM, Steelcase, Knoll, Humanscale etc. are more durable overall, they're much more comfortable and adjustable, they look better, warranty protection is better, they're more repairable, and they're pretty much all American made.