I bought a used Ikea "Jerker" (no, I'm not joking) on Kijiji a couple of years back for work as they no longer make it anymore. Does the job nicely. It is NOT motorized or adjustable (without unscrewing the whole tabletop and/or shelf) once you get it set for your preferred height. To make up for this, I use a high drafting chair when I'm not standing.
Here's one for sale in Calgary right now (no, not mine!):
http://calgary.kijiji.ca/c-buy-and-s...AdIdZ557860722
I find that I stand for about 75% of my day. My primary reason for getting it was because I had some hamstring, hip, and groin issues from old soccer injuries, and physio suggested sitting less in addition to some other things. And because I'm a paper-pushing keyboard jockey, a standing desk was my solution. I think that it has helped me somewhat, and I wouldn't switch back to something more standard. I often find myself leaning on the desk doing stretches with my legs while I read things online. In my office, I don't care what I look like because we don't get visits from the public or clients, and I could care less what my colleagues think as it is a small office. Depending on your setting, you may want to refrain from sticking your ass out to stretch your hamstrings while reading CP, or embrace it as I do.
For comparison sake, based on the side photo on the Kijiji link above, I have the shelf part on the 4th setting from the top and my monitors sit on that, and my desk is at the 10th setting from the top. I'm 6'1 and this is comfortable for me, but that will give you a rough idea of how much you can go either way if you need to.