My Geek Desk showed up last week!
I work standing up most of the time, but I do like to sit down a few times through out the day. In the past I used a "Drafting Chair", but they create a funky angle for your legs as your feet must sit on the bottom ring. So far I am really loving the Geek Desk! - check them out at http://www.geekdesk.com/
here is a short vid of the adjustable height desk in operation
and some pics