that doesn't really seem like an adjustable desk. from the title i thought it was a cheap version of something like http://www.geekdesk.com/
i use an ikea jerker desk set to its maximum height for standing at: http://www.flickr.com/photos/symmetricalism/5488994391/
and when i need to sit, i have a drafting chair that is adjusted high up for the desk's height: http://amzn.to/fZLkPQ
This is the desk I'm using: http://madeonjupiter.com/llegs-desk/
no slide-out trays or side trays, but the desktop can be raised up to standing height.
If you look at this pic you'll see the tabletop plus two shelves. The shelves and tabletop can all be mounted at different heights. I mounted the shelves below the tabletop and my tabletop is at 104cm but can go much higher.
The physical benefits are that my ass doesn't hurt nearly as much and my back feels better (if I am careful not to slouch) .
I also feel there is a benefit in terms of the "take-a-walk-and-get-a-good-idea-effect". I'm not sure if there is any science behind this, but I feel that I can think more clearly when I am walking around away from my computer. I've found part of this benefit is acquired by just standing all the time. When I'm in the zone, I don't have to take a break to get up and walk around.
If you're considering trying standing at your desk, try it out for a week by piling up the books by your desk.
Be warned though, one negative is that people definitely come over and interrupt more often. I think the fact that they can see me standing (and no one else) from across the office gives people the impression I'm only casually involved in my work at the moment.
 At first my feet really started hurting in the afternoons. I bought a fairly expensive floor mat (e.g. gelpro) and this has really helped.
Ignore the text about a maximum of 20lb. When you get it, it's actually a MINIMUM of 20 lbs required. 20lbs is the balance point: if you have less than that, it stays permanently up. But if you have less than 20lbs you can take out one of the springs. Of course, most woodworkers using it for it's intended purpose use 20lbs of hardwood, but I use a jerry rig that's much lighter. Then I added a 30lb 30" monitor, and it works great. The springs lift 20lbs, so you only have to put in 10lbs of effort to lift 30 lbs.
I'd worry about adding a lot of heavy weight to the front of it where there is more leverage, but I wouldn't hesitate to add another 50lbs to the back. This thing is solid.
Of course, it's a fixed travel distance. But if your monitor also has a little bit of height adjustment as well, it'll work perfectly.
P.S. When sitting, I have my desk 1 - 1 1/2 inches lower than "typical", primarily to provide a better typing position.
If you think you need more than 12 inches you're slouching while you're sitting.
But when I stand, I stand up straight. Or at least I slouch less.
Just checking now, I've got about 18-inches difference between my seated keyboard height and my standing keyboard height.
META: why is my 5 ranked post at the top? There's more interesting posts more highly ranked further down. Because it has more comments? To those who care, I think `javan`'s post is the most relevant for somebody looking to make a cheap & easy desk.
Just a warning: I've found that the more I stand, the less I like to sit. Going to class (I am still an undergrad) has become annoying for entirely the wrong reasons...
I used a cheap black table top from the desk area. I'm happy with mine. When I need to sit I find a different surface, or use a taller stool.
I use this ballpark-vendor like laptop holder sometimes: http://www.thinkgeek.com/computing/bags/a988/
The big problem is you have to crane your neck down.
I am trying out an artist's easel for a standing desk. Cheap and portable. I Can hold the monitor while I use the connect-a-desk for my keyboard.
It takes like 30 seconds to move my desk around, I'd be kidding myself if I could justify a $800 desk (if I could even get it in AUS) to save 30 seconds a few times a day
I'd like to build some small shelves off the sides of the top level to add some speakers, but beyond that I've been extremely impressed with making the switch.
I guess I'll stick with my "free" standing desk for now - made by stacking 2 existing tables in my parents' basement: http://d.pr/CG9n I even get double the surface area for storage on the lower level!
I find it really jagged on scrolling and generally annoying enough to be distracted from the articles. Also, what looks like a link to turn it off and go to the old site doesn't work.
I spent about $50 on several 2x4's, two pine planks (48" wide x 16" deep for the monitor/laptop, 36" wide x 16" deep for the keyboard/mouse platform), miscellaneous bolts and some poly stain. I'm now using my computer while maintaining proper posture for the first time in as long as I can remember. I plan to buy a $39 'drafting' chair from Walmart for the occasions when my feet hurt.
One important element, by the way, is the fact that my laptop screen and external monitor are truly at eye level now. This has done wonders for my neck. I think this is a major flaw in the linked desk design.
Oh, and it's occurred to me that I could probably design a very functional stand-up desk requiring nothing but Ikea shelving parts, a saw, and some bolts, probably for under $40.