I'm also fascinated with the downsizing movement. My wife and I are in the early stages of moving out of a 3,700sf house that we've lived in for 20 years. We haven't determined exactly what size we will end up in, but I suspect it will be well under 1,000sf, a modest goal by most downsizer's (is that what they're called?) standards I know, but still a major step for us.
If everything comes together we will be building a small apartment above a family members garage. I think we would be very comfortable at anything over 600sf or so. You talk about getting rid of a lot of stuff! Married for 47 years and in this large house for 20. It's going to be quite the triage process: throw away, give away, sell and keep.
I'm definitely not very hardcore at this though as I have no plans of getting rid of my AS. But spending four months in it this winter in it demonstrated to both my wife and how just how comfortable and happy we can be in a small space. I actually prefer it over my house.
I started my first baby steps in this direction by severely restricting my buying a couple of years ago. If it's not there it doesn't take up space, you don't have to take care of it, you don't have to worry about it, and you don't have the hassle of getting rid of it when you no longer "need" it.
The less is more philosophy seems to be growing rapidly in the U.S. I imagine some of it is simply adapting to increasingly difficult economic conditions, but I think some of it is practical and philosophical in nature as well. Not for everyone, but as an old guy it appeals to me.
John & Vicki
Grown men don't need leaders. ~ Edward Abbey