[jackalope]

...I don't think I would be any happier standing continuously than sitting continuously.

I came to the same conclusion after switching to a standing desk for a few months.

Now I'm using a yoga ball and it's amazing. It's immediately intuitive: just sit on it and shift to another comfortable position if you've been in one place too long. My core is even getting stronger from balancing (although it doesn't feel like a workout). I have a 65cm one for desk-height and a 75cm one for counter-height. I highly recommend it.