I tried a standing desk for about a week and a half. The theory was that it would make me healthier and fix my unfortunate obsession with sitting in front of a computer for extended periods - unfortunate, that is, for my long term survival prospects. In practice I really liked the style of standing up in front of the computer and found doing work or goofing off that way was comfortable right up to the point where my knees started aching. After about four days of just sucking up fairly substantial discomfort I took the box off the desk and went back to a chair. I obviously need some more elaborate arrangement in order to have a standing desk that works, perhaps something where I raise and lower the desk regularly so I spend no more than an hour standing or sitting in a row.
For me it seems lifestyle improvement projects are easy or hard mostly on the basis of time. Cutting back on sweets wasn't hard because it didn't interfere with my obsessions and just required me to substitute eating a carrot for eating a cookie. Adding exercise into my routine is bloody difficult because I need to stop doing things that are awesome (killing pixel enemies and taking their stuff) and start doing things that are boring (yoga, pushups, running). The standing desk was the same, pretty much, because I didn't mind the effort of standing while at the computer but I sure did mind my knees hurting enough that I just couldn't do so anymore.
I need some kind of stair climbing machine or something that allows me to do a serious workout without interfering with my endless desire to soak up information... also without destroying my knees. I am part of a generation that has the realistic possibility of extremely extended lifespans and I fully intend to live long enough to see if that pans out; I must find a way!