let us not overlook those who stand while at the keyboard. you don't have to do it all the time, either -- get an adjustable keyboard thingermajig and push your chair out of the way for a few hours a day.
Still pretty pricey at $549 for just the frame. (Luckily its compatible with IKEA tops)
I wish IKEA would bring their adjustable legs back to the US, since their desks are so customizable.