I've been trying to find a really comfortable office chair for ages. I used to use one of those kneeling chairs, but found that the pressure on my knees was too much after a short period, even though the chair kept my back in a comfortable and natural position. Since we moved, I've been using our landlord's standard office chair, but I don't find it comfortable and my shoulders and back are beginning to suffer.
I came across the Bambach Saddle Seat, and really liked the idea. I used to ride when I was younger (with an enjoyable return to the saddle in Brazil), and I always found sitting in a saddle very comfortable and natural. I seem to automatically sit up straight in a saddle, with my shoulders relaxed and pushed back rather than rounded forwards. Of course, it could just be a conditioned response to all those years of my slightly frightening riding teacher barking "Sit up straight! Shoulders back! Chest out!" at me like a Drill Sergeant. So the Saddle Seat looked ideal, but I really didn't have £400-plus that it costs.
Then I saw the T2000 Saddle Stool at Natural Living: it seemed to be a very similar design, lacking some of the adjustability of the Bambach Seat, and perhaps slightly less high quality in finish, but only £99 including delivery and VAT. I got some money for my birthday, so I ordered one; we'll need a new office seat when/if we move house anyway. I've been really pleased with it. I felt immediately at home on it, and I find working on the computer so much more comfortable and natural. My shoulders and lower back in particular don't complain now, and because of the way that you sit astride the stool, it doesn't restrict the circulation at the back of your knees the way that standard office chairs do. Because there's no back on the chair, your upper body is much more mobile, and I find myself twisting around to reach things behind me, which must be a good thing for the mobility of my back. It even seems to have improved my typing accuracy!
Above all, it's just fun to mount your saddle when you get down to work. When I'm reading from the screen without typing, I've taken to resting my hands on the 'pommel' of the saddle, as if I'm surveying the herd out on the plains. If no-one's around, I might even 'gallop' my saddle stool across the laminate yelling "Giddyup!". I just wish I could get one for work too.