A few months ago I bought a NextDesk Terra standing desk and wanted to pass along a update on my experiences with it. My original post on it is at http://blog.dougtoppin.name/2014/09/07/nextdesk-terra-standing-desk-opinions.html.
I have had no complaints and for the first time today needed to use it from a sitting position. Being able to quickly send it up/down to the position that is most convenient is definitely an advantage. I have had to get used to a little slight movement because of it having 2 vs 4 legs but that has not been an issue.
One thing to note is that because it has a power cord you need to plan for how you are going to run that to an outlet. If the desk is not directly against a wall then the cord should be placed in a way that you will not trip over it while walking around it.
Also, while in a standing position use a comfort mat was necessary for me. It makes a noticeable difference in how your legs and feet will feel after a few hours of standing. Something to note about that is that when in a sitting position you may not want your chair rolling on the mat so you may need to plan to easily move the mat to and from the desk when you want to use it.
The bamboo surface is subject to dents so you should be careful about dropping or banging stuff on it. I have had a few dings but am still satisfied with the surface.
All in all I recommend it and no real complaints so far.