I used a dining chair for a while and it was ok. It got the job done. But then I got a "proper" office chair and I would never go back. My only regret is that I did not make the purchase earlier.

Before purchasing a chair, I went to an office furniture and tested several chairs and had the employee point out why people preferred different chairs. In the end, I got an Aeron. Also, it comes in 3 sizes and I made sure to get the correct size for me.