I've used this sleep schedule before. It's extremely liberating, if only a little lonely at the beginning of each week.<p>It's not hard to switch back and forth as long as you use one of the bedtimes that's normal for both schedules and just wake up with an alarm when you're supposed to on the new one.<p>The best thing about it was that I was actually tired (on the 20/8 variation) when it was time to go to bed, and I usually woke up a few minutes before my alarm starting on about the third day. These two phenomena never happen with any variation on a 24 hour day that I've tried. I was more productive (got my normal work done; started cycling regularly again; wrote more; and was averaging 2-3 books per week) and happier. I can't think of anything bad to say about it except that the last few hours of each "day" are a bit sluggish. I'm convinced that helped me sleep.<p>The only reason that I went off it was because my girlfriend has a fairly restrictive (yet changing) schedule. I was looking at not seeing her at all for a week if I continued it.<p>I should say that if I just go to bed when I'm tired, my body defaults to something pretty close to a 28-hour day regardless of light levels and the other people I've known to try it had negative experiences.
I did this without really planning it during my break between high school and college. I really enjoyed it, but it's not really practical if you have a "normal" family life.<p>It's kind of analogous to a lot of good software ideas, that would be amazing if only everything else were compatible.
The thing I don't like about alternate sleeping schedules is they usually include, as this one does, a warning to stick to it and go to bed at the set hours even if your not tired.<p>Personally if I was going to embark on this I wouldn't be very formal about the timing and just sleep when I got tired. I guess another thing that makes a big difference is if you have somewhere to sleep that you can make mostly dark during the day or will you frequently be going to sleep in a light room.
I had an officemate back in the mid 90s who was on this schedule for several years (he was a researcher able to set his own schedule for office time) and it worked quite well for him. He seemed to enjoy it and talked at length about how it was closer to the natural circadian cycle for people (which is a claim I don't know about.)<p>He did great work during that period; obviously this is just another anecdote but there you go.