I bought my HCH-II on the 16th. The first day and a half, I was only getting something like 40-42 mpg, but that was before learning about and using any of the special hypermiling techniques.
After reading Tarabell's article
on CleanMPG.com and using all the new techniques I didn't know about, topping off my tank, and resetting my Trip A, I've been able to get my MPG way up. Pulling into my parking garage at work today, I had something like 600 mi on the car, and for the past 230 or so since the reset, it's reading 51.8.
Most of my commute is highway, and I've actually noticed I do better on the highway, than on the back roads. Both highway and backroads around here are VERY hilly. My whole ride to and from work is nothing but up/down hill (very large hills), where I have to unfortunatley push my tach up to 2,500 - 3,000 to keep my speed above 50 when I near the top of some of them (starting off doing 65).
Although there is some city driving I could do in my area, I haven't had the need to test it out, so I don't know if my practice of the techniques would be as good off the highway.
Hope that helps you out some.