So I've been thinking about it for a while. Articles like this one: http://www.popularmechanics.com/technology/gadgets/reviews/walking-while-working-should-you-try-a-treadmill-desk-13336477 speak of the benefits and improved health that can be a result of having a treadmill-and-desk combination. The idea is that you walk slowly enough to be able to type and mouse (1-2 mph) because even a slow pace is way better for your body and joints than sitting or standing.
With my job I don't often work for 8 hours solid on the computer, but I do often work for more than two hours at a time on my home PC. It also can be wayyy too easy to justify working/playing on the computer rather than getting out and exercising. While I haven't yet done cardio (getting out of breath and significantly raising my heartbeat) on the treadmill desk, I have already found myself here (yep, I'm using it now!), walking and burning calories instead of just sitting.
I'm thinking it will also be nice for when I'm reading or on the phone, though I have yet to try that. I've tried going for a walk while I'm on the phone, but if it's even a teensy bit windy out it becomes a less-than-lovely experience for my poor phone buddy. I've never bought a significant piece of exercise equipment before, so let's hope it's not a regrettable purchase!