At first, I didn't think I was going to be able to, but after mentioning the idea around and getting amused-but-positive feedback, I'm now walking at work again. I'm in a cubicle, but I'm kind of stuck back in a corner. So there's really only one person who can hear the treadmill and he said he didn't mind since he usually wears headphones anyway.
My setup is basically the same: same treadmill with keyboard, monitor and trackball on a raised desk. The cube is furnished with this modular furniture that attaches to the wall, so I just had to attach the main desk at the correct height.
The one main difference is my cooling setup. Before, I had two, sometimes three, fans blowing on me as I walked. Here, the entire building is on
raised floors with the air conditioning being pumped under the whole floor and then into the office via vents in the floor tiles. To keep me cool now, I've just found a couple extra vented tiles and put one on either side of the treadmill, blowing cold air on me on both sides. I've found that if I'm not walking I actually need to cover one of them up or I get really cold.
In addition to walking, I'm trying to get back into eating better. Basically, I'm just going back to what I outlined in
this post way back when.