Let's start with the seat-back: pure mesh, with no support beams of any sort that might dig into your back. The seat-back's structure comes simply from the seams of the mesh's three-panel construction, giving the back its shape, its firmness, and its ability to conform to your body. As the Aeron previously showed us, mesh is not only attractive but reduces the chair's weight and increases its airflow (perfect for those who tend to have sweaty backs).
Me, I'm a constant recliner. There's some evidence that reclining is the preferable posture for spinal health. The further you recline, the more your weight gets transferred from your spine to the chair's back cushion. I looked for a fully reclining office chair (a design known as "zero-gravity"—like the position astronauts sit in), but it seems everybody stopped making them about five years ago (you can find zero-gravity chairs for the home here). Even though it's healthier, and for some might be more conducive to high productivity, full recline has failed to catch on—no doubt because it just looks too lazy in an office setting.
Anyway, my fellow recliners will adore the Liberty. The joy of this thing is in its lean. As your shoulders go aft, the chair-back tilts itself so as to press forward against your lumbar region (instead of leaving an unsupported gap there, as most chairs do). No matter how far you recline, the Liberty never feels at all tippy.
And, there are no knobs and levers to contend with. The Liberty is designed to use your own body weight as a counterbalance. You needn't adjust any tension settings—just lean to whichever angle you like, and the chair will comfortably stay there. It feels natural, like it's an extension of your spine.
The total lack of adjustment knobs makes a ton of sense. Most people are not the first to use their office chairs. By the time you get a third-hand chair, the settings have been messed with hundreds of times and the instruction booklet is long gone. Even if you manage to figure out what each lever does, you often feel unsure of yourself—with so many possible adjustment permutations, you always suspect that you've chosen a suboptimal mix.
My one complaint with the Liberty is that they took the anti-knob mania a step too far. There are no adjusters to raise or lower the armrests. This can be a problem when trying to pair the chair with higher or lower desk heights (or for a person with a particularly long or short humerus).
But this is nitpicking. Here we have the Aeron's logical successor. Every bit as sleek, without the superfluously techy features. The Liberty was the most expensive chair I tested, but in this case, it's well worth it to pay a bit more for the good sit. Put that Aeron on Craigslist, and slide your moneymaker into a Liberty.