I have the LifeSpan TR1200-DT5, and it's quite lovely.
I get on it in the early morning and mid-day when I'm a bit sleepy, for 3-4h/day total.
1/2 MPH (slow crawl) permits you to use the mouse reliably and keep your shoulders level so that no one knows you're on a walking treadmill during a conference call. This is way easier to do than just standing... I can do this for hours without pain or fatigue.
1-2 MPH (steady walk) permits you to do reading and typing without any problem. I usually go 1.5, and then only for a half hour at a time -- but then again, I'm kinda lazy.
3-4 MPH (brisk walk) permits you to close your eyes and get out some frustration when it's cold outside, take a call with a colleague, or, read non-intensive (Hacker News) material. My knees hurt after a very short while... so I hardly ever do this.
The lifespan's desk has a built in arm-pad that really, really helps the movement/shock so that you can type ... even at 3MPH. If I were to buy it again, I'd get the more expensive model though, I find myself lubricating the track all the time and it's irritating.
> This is way easier to do than just standing... I can do this for hours without pain or fatigue.
Thanks for the response. I also find standing to be be incredibly fatiguing and not really a workable solution, so I was wondering if a treadmill would just be the same thing, but with a much larger investment before learning that it wouldn't work.