I'm sure standing 24/7 isn't going to be healthy, but neither is sitting 24/7. I imagine the optimal amount lies somewhere in the middle - not too much sitting, and not too much standing.
I'm not planning on spending my entire day on my feet. Probably an hour standing for every hour of sitting, or thereabouts.
I've also ordered an anti fatigue mat. Supposedly they help a lot.
I've had a standing desk for almost 18 months now. A few things.
1) You aren't standing 24/7. I mean I know that's not literally what you meant, but even if you "stand" for 8 hours from the time you get there to the time you leave, you are still walking, having meetings, etc.
2) It's not the standing..... it's the standing STILL!!!! (yes 4 '!'). Your feet, shins, knees, etc hurt because standing still they all have zero blood flow (well, at least horrible blood flow). A padded mat attacks the symptoms, not the problem. The answer? Move the fuck around... Here's a fun fact.. Standing still at a desk your knees get sore as shit after say two hours.... instead of sitting down, do like 5-10 ass to grass air squats... guess what? Your knees IMMEDIATELY AFTER feel fan-fucking-tastic. You just need blood flowing freely and happily through your shit.
3) sitting is in no way "out of the question". Instead when you sit, enjoy the fuck out of it. Seriously, you were just on your feet (standing, walking, jumping, squatting, whatever) for like 1-8 hours.. enjoy taking a load off during work for 5-10 minutes, and honestly enjoy it. I usually take "cigarette breaks" in my cube sitting down and reading on my phone or my ipad... if fucking smokers can stand outside and kill themselves for 10 minutes and it be alright... I can enjoy some quality sitting time while reading a comic or blog..
4) do it right... take measurements.. make sure your monitor is at a good eye level, keyboard is at the right height.. stand with good posture.. don't slouch and at the same time make sure you are not hyper extending your back (sticking your butt and shoulders way back). lay on a hard surface flat with good form.. take notice of your body/back.. this is how you should be standing also.
we are moving buildings after the new year, and I've already told them the new cubicle arrangements better support standing like our current ones do.. I am one out of a few hundred employees moving, so I know where I sit among the sea of things.. still, if the new cubes don't support it, I'm going to have piles of books, boxes and magazines hoisting my shit up because I am never sitting for work again. the human body just wasn't made to sit for the vast majority of 8-16 hours a day.