TL;DR
I have been using a kneeling chair for years now. It's great for me, and I recommend it.

I was using a regular office chair until several years ago. Then I got carpal tunnel syndrome (not officially diagnosed, but I had all the symptoms). Also my stance was hunched, both while working on the computer and possibly as a result, when standing. My whole arm start hurting, all the way to the shoulder. It became unbearable so I went to my healthcare provider and got physical therapy sessions. That didn't work, so I tried acupuncture, which didn't work either.

At that point I started thinking "out of the box" and paying attention to my stance and sitting position. I saw it's all bent, so I started trying to force myself to sit more upright. There was some success with that using a regular office chair, but I noticed I'd fallback to slouching without noticing. So I got myself a shoulders strap, one of those which pull my shoulders backward. This helped but, still I noticed there's space for improvement because I'd get fatigued by pulling my shoulders back while sitting. That was the point I decided to give a kneeling chair a chance. At start, it was difficult and uncomfortable. I couldn't sit long, and my knees would hurt. I did notice my back didn't hurt thou, because the kneeling chair forced my back into an upright position, and maintaining this position was quite effortless. So I decided to give it more time. Little by little, my knees got more accustomed to the position. Also, I realized that I can straighten one knee at a time by sticking my leg in front of the chair or bend it and have the foot flat on the floor (then alternate with other foot).