I have a Herman Miller Aeron with PostureFit. I used to sit on one of my wooden kitchen table chairs all the time and always had lower back pain. A good chair is expensive but well worth the cost.
I bought the Herman Millar Mirra - the version down from the Aeron - about 4 years ago.
Was it worth the cost? Yeah, yeah it was.
Ignoring the ergonomic benefits, it's just a damn good chair. It's very comfortable. The tilt options are particularly good. I've been known to drag it into the living room to watch TV on if I'm having a bad posture day.
And the lifetime guarantee is really nice, and appears to Really Mean Lifetime. The seat started going about three months ago - I phoned HM up, and a new seat turned up in a truck about a week later.
I can imagine not buying another chair for 10-15 years or more, and at that sort of timescale, it's a bargain.
I enjoy mine. It's solid and comfortable. I got it on Craigslist for $300. A company was going out of business and had a bunch of them to get ride of. You might get lucky like I did.
At my office we have the Human Scale Freedom's which are also comfortable, but not as adjustable. We've had 2 break (1 arm rest, one handle on the back) recently, but other than that they are great chairs.