This is why I got my department to buy me a GeekDesk a couple of years ago.
We've been using Kangaroo desks. We went to them after trying out a few Ergotron sit-stand desks that were just too flimsy.
We've got about a dozen now and there have been nothing but positive reports including a few that have lost weight (not a controlled study). The best tool we've found for making sure the desk gets used is to have your PC read off the time every half-hour as a reminder to switch. I don't have one of the desks, but I use the half our reminder to get up and move around if I haven't recently.