One thing I noticed about my mileage in the time I kept track, was that even with the regenerative braking, mileage still suffers the more you start and stop. If I got out the door before traffic started filling in, and could time lights and coast to lights, I had much better mileage than otherwise. It is dramatic, and I think if everyone had instantaneous and daily mileage instrumentation, even without a hybrid car, they'd be shocked at how much their mileage suffers in stop and go traffic.
One day the mileage might be 56 or 57 MPG, and the next 45. That is a huge % variance, and just because of "bad luck" in traffic and maybe a cooler day with the defrost on.
Now that the administration has set some serious mileage goals for the next decade, it should be interesting to see how the manufacturers chose to meet these targets. We'll see more hybrids, but I think so much can be improved by better instrumentation, which I think will drive people's driving habits. I can't tell you how many times I'd see the light ahead turn red, start my coast, and have cars zoom around me to then slam on the brakes at the light. Sometimes, I'd even pass them up without stopping if I happened to be in the lane that cleared quicker.