In-depth: Kangaroo Desks
If there's one thing I would recommend to someone with AS and an office job, it would be a sit / stand desk. The ability to quickly and easily change your posture through the day from sitting to standing makes a massive difference. I use them every day now, and can work for much longer than I used to without a break. Even though I usually don't stand for long (20 - 30 minutes and I'm ready to sit down again), the point is not to stand all day - it's to give your body different postures to shift from and to through the day, staving off pain and stiffness.
At home I use a Kangaroo Junior from Ergo Desktop. Project Ergo have given me another model called Wallaroo Junior to try out and compare (thanks David!) so here's an idea of what it's like to assemble and use one.
Wallaroo Junior - Assembly
One thing I like about these desks is they're simple pieces of kit. Pictured is all the components. The base plate (the curved black plate lower right) is solid steel so is very heavy (with rubber coasters so it can easily slide without scratching) - the idea is this gives the unit stability without needing ugly clamps to attach it to your main desk.
The hardest part of the assembly is attaching the main strut to the base plate. However even this is pretty easy if you have a corner desk to work with - let it hang over the corner while you screw in the bolts.
Nearly done. There's a couple of simple bolts for attaching the shelf / work surface which slide on really easily.
Now grab your computer screen and screw the VESA plate onto the back. You can then simply hook your monitor onto the main strut. A little adjustment to the screen height if necessary by loosening / tightening 4 bolts with a spanner (supplied) and ... you're done! The desk goes from sitting to standing simply by releasing a brake knob to allow the pneumatic piston to slowly raise the unit up.
Comparison with Kangaroo Junior
The main difference to be aware of (and this is why the Wallaroo is slightly cheaper) is that the monitor height on the Kangaroo can be easily independently adjusted using a simple brake knob - meaning that you can alter the height the monitor is above the black work surface really easily. You can do this also with the Wallaroo, but it involves removing the screen and getting a spanner out, so not something you can do easily.
However for me this isn't important as long as you have the correct height desk and chair. If you have your desk and chair at exactly the right height, you won't need to adjust how far the monitor is above the work surface when you change from sitting to standing, because the distances and ratios should all be the same.
A bonus is that the Wallaroo Junior monitor mount can swivel - this is great for working in teams as you can easily swing your screen around to show someone. However again there's a minor downside to the swivel mount - because it's a much larger mount than the Kangaroo it 'pushes' the screen about 6 inches closer to your face. I found this was a bit too close for my liking. For this reason I would recommend getting the Wallaroo standard (not junior) which has a deeper work surface, and the monitor will be at a more comfortable reading distance.
I like the swivel mount of the Wallaroo and have no need of the independent monitor height adjustment of the Kangaroo, but the screen distance is an issue. I would recommend the Wallaroo (not full version, not the Junior) due to it's deeper work surface.
Get yourself an anti-fatigue standing mat made of bio-foam. It feels fantastic to stand on without shoes on, and I find my calves don't get tired as quickly.