When I get home and is exhausted with my back and whatnot killing me, where do I go? Not to the couch and not to the bed; I plump down in my Aeron chair to get relief. Mine has the old lumbar support, but I'm looking into getting the new "posture fit" back support thing; I tried it in the store and at least for me it seems much nicer.
Regarding the bad review here, I suspect the reviewer didn't put in the time to figure out the best settings or -- worse -- keeps the chair too high and didn't get a foot rest. You can't have your feet dangling in the air, that'll mess you up no matter which chair you sit in!
There are many good chairs now competing with the Aeron, some of them cheaper, but at least for me there's no doubt it's so worth it.