I like to be above the sewing, and so I use a drafting chair (has wheels and is height adjustable) for most of my piecing and FMQ. I have some back issues, and find that a very high chair alleviates the pain, which means I can sew for longer. Being higher up also helps me not get that knot in my neck that seems to happen when I sew for a long period of time. There are times when I use a lower office chair, but not very often any more.
The disadvantage is that you can't get your knees under your sewing table, but that doesn't bother me at all. I kind of prop myself on the edge of the seat. However, if you are thinking of getting one, it might be a good idea to see if you could try one out. A couple of my friends tried mine and said it was not for them.
My theory is that if I can have more than one sewing machine, I can have more than one chair.