You are correct: it's a fairly slow walk around the neighborhood. Typically I average between 3.5 and 4 when strolling around outside.

That being said, it's fast by the standards of treadmill desk usage (judging by what I've read and a coworker that bought her own treadmill). I can't speak authoritatively but the impression I get is that most people walk around 1.0 mph which is maddeningly slow for getting around, but appropriate for mindlessly pacing while typing or talking on the phone.