I've used a variety of modern office chairs in offices. The Aeron is decent, but I also saw a lot of them break.
What I've used for years is an old quartersawn oak steam-bent office chair. Found it for $35 at a junk store and refinished it myself. Solid oak might not sound comfortable, but it's the only thing that I've found comfortable for long hours.
Most have been plucked out of junk stores these days, but running a search for "antique office chair" on eBay will pull up quite a few. They don't have to be oak - you'll find them in beech, walnut, ash, and several other woods.
A side benefit is that these hold value and appreciate. Ten years on, it'll be worth more than you paid for it. Most new office chairs won't be worth anything.