I use to sit in an Aeron chair for years at my old job. To be honest it was just ok.
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I ended up getting a chair from office depot/max the workpro 1000... reason why I like it, is because the seat can adjust forward and backwards making back support with more pressure than an aeron chair had.
Wonder if you had the fully adjustable model or the base model of the Aeron. The fully adjustable can adjust the seat angle forwards/backwards to have it such that you sit into the back more firmly or less so. You can even set the angle in which it will stop reclining (i.e. if you want it to only lean back a couple of degrees, you can set that, and you can increase/decrease the force it takes to lean back). Again, it all depends on the options on your chair. Previously to keep things simple, there was at one time a model that was simply called "fully adjustable" which essentially meant it had all the features. Now looking at their website, you have to select all the various options (i.e. adjustable back support, tilt limiter and seat angle, fully adjustable arms, and then obviously the seat size/color/material).
Comfort aside (you need a chair that fits your body, so all things equal with a chair that fits you), to me, the real reason was the 12 year warranty. I was so tired of buying a new chair every 1-2 years as the foam/padding/mechanics broke-down and spending another $200 replacing it... If you have a problem, just call them up, and they will confirm the chair is still under warranty and send out a repair technician to fix it (yes you read that correct, they will send the tech to you, not you sending the chair back to them). I had them come out once to fix the back support which broke, they also took a complete once over of the entire chair since they were there, checking all the seals of the pneumatic cylinder and bearings and all the controls and webbing for stresses that might need to be replaced). Good luck with most other companies if you have a issue (usually you will be without your chair for 2-4 weeks while it is being serviced/repaired if you are even under warranty after finding a way to box it up and spend $50 to ship it.. they hope the hassle and expense is enough that you simply say screw it and buy another chair).
Mine is well out of warranty now, but I more than got my money's worth and it is still functioning without problems. Again, you still need a chair that fits your body, and for some people the Aeron isn't the right fit (about the only place you can not adjust is the depth of the seat other than in the sizing of the chair).