I switched to a standing desk almost a year ago. Didn't take me long to decide that I wanted a nice thick gel mat to stand on. No, not a yoga mat. Something really thick and cushy, made for this purpose. (My 8yo daughter thinks it's awesome BTW.) I have also always taken breaks and switched to using my laptop on the sofa or loveseat for a while. It's also worth mentioning that I have a freakishly strong lower back. Maybe something to do with slinging 40lb boxes of books around a lot when I was younger. Anyway, when I used to frequent health clubs I'd always push 20% more on the lower-back machine than even the most hard-core lifter types. And I still get a sore back if I stand too long. Just don't do that to your body all day.
More recently, I switched from my ad-hoc pile of boxes to an adjustable-height desk (Ergotron Workfit-S). It's freaking awesome. I can switch between standing and sitting almost effortlessly, which makes a huge difference. Now I've settled in to a rhythm of standing 65-75% of the time, and sitting the rest, without ever having to break my concentration. It's really a lot better than either position alone, or expensive "context switches" between the two. I highly recommend trying it. If you don't like it, you can just leave the stand in your preferred position permanently.
More recently, I switched from my ad-hoc pile of boxes to an adjustable-height desk (Ergotron Workfit-S). It's freaking awesome. I can switch between standing and sitting almost effortlessly, which makes a huge difference. Now I've settled in to a rhythm of standing 65-75% of the time, and sitting the rest, without ever having to break my concentration. It's really a lot better than either position alone, or expensive "context switches" between the two. I highly recommend trying it. If you don't like it, you can just leave the stand in your preferred position permanently.