I had trouble finding a decent chair, so I switched to the IKEA Bekant sit/stand desk. I work standing for about half the day, so if I'm having issues with my chair at least it's not for the whole day.
I really like it. It's a bit pricey for IKEA, but compared with other adjustable height desks, the price seemed quite good to me. Also, since it looks like what you would expect from an IKEA desk, it blends into the room nicely. It doesn't look as utilitarian as some other desks might.
