About a month ago, I bought a used Steelcase Criterion chair from an office liquidator for $120 (I believe it was Portland Office Furniture). I think the retail on these was around $800, and mine was in great condition. It looks like an ordinary office chair, but it's super adjustable. Seat height and back height, of course, plus arm height and arm width, overall tilt, seat position forward/back (it slides), and back tilt adjustment. Unlike any other chair I've ever had with a tilting back, this one can be locked in a properly upright position.

As you may or may not recall, I built a standing desk and was using that for about six months. It helped, but my neck/shoulder pain continued.

Three days after getting this Criterion chair and having proper elbow support, my neck started cracking like crazy. For the first time in three years, my neck muscles were able to properly relax. I'm sleeping on a normal pillow for the first time in two years.

So, my conclusion is that adjustable elbow/forearm support is absolutely critical. This goes against all of the old ergonomic literature I've read. Also, upright posture is very important, and you can't achieve that with a chair that lets you sag backwards.

Since most of HN is quite young, I'll do the old guy thing and give a stern warning: you may not have any problems now. You probably think your back and neck will be fine. And you might be right. But here's the thing: you won't know whether you're susceptible to these sorts of injuries until you develop one, and then it's too late. And by the way, stop slouching. ;-)

For those who haven't looked into it, you can usually find a good, used chair on Craigslist, from a liquidator like I did, or from a private party. Aerons go for $400 - $500, if you can get one for $350 it's a fantastic deal. Criterions go for $100 - $300. The Steelcase Leap is usually $300 - $500. All of these chairs are ridiculously durable, and replacement parts are available.