Considering the fact that my commute to work is an hour each way and that I live an hour from grocery stores and shopping, I don't think it would be practical for me. If I lived in a more metropolitan area, sure, I'd try it just for the exercise.
I have done it before, even biked and skated long before I had a vehicle. Sometimes we take them for granted but having to walk everywhere while good exercise will take quite a longer time for just about any task.
Seeing how I live 3 blocks from where I work, where I can also shop, I definitely don't need a car. I can walk there very easily and do from time to time for the extra exercise. My daughter however is 15 miles away so, in this part of the country especially, walking is out of the question.
What a great concept. If you live fairly close to your job, grocery store and shopping, it would work well. Like most of you, I live in a rural area and drive about 20 miles to work every day. Don't think I could walk it and get to work on time. City dwellers would have it made though.