If you've been thinking about getting a walking desk, do it!! I bought this TR1200-DT3 treadmill base and got a standing desk from another company and am loving the combo. (The standard LifeSpan desk that can be bought with the treadmill wouldn't work for me without lots of addition$ to raise up computer monitors to eye level, etc.) The treadmill is solidly built, super quiet (my footsteps make more noise), and as sturdy as anything I've used at the gym.
Working and walking felt a tiny bit awkward for the first 30 minutes or so and after that I kept forgetting I was on a treadmill. I'm typing this at a leisurely 1.1 MPH pace and can pretty much do everything walking that I can when sitting at a desk.
I'm a grad student and work part time from home for a software company and was sitting way too much. I don't have as much time to go to the gym these days, so this is a great low-impact way to stay active, sneak in exercise, and help beat the mid-day energy slump. I'm really happy with the treadmill and am looking forward to using it for years to come.