After all the discussions HN has had on this topic, I'm still waiting for someone to pop up with "Yeah, I've been doing this for two years now and I'd never go back." So far the stories have all been in agreement... "it sort of kind of worked for maybe a month or twoish (with rare people sticking somewhat longer), then I hit a wall because I was ever so slightly bumped off the schedule and I just fell apart. Also in hindsight I realize that I wasn't doing as well as I thought I was at the time."

So far I'm not seeing any concrete evidence that the general idea of polyphasic sleep is anything but wishful thinking. I recognize that anecdotes are not data, but after a while the complete lack of even anecdotes of success, after the number of people trying it publicly, is itself evidence of a sort.

"Biphasic", or "afternoon naps", by comparison, are indeed quite natural, though I'm not sure I've seen that much convincing evidence that night sleep+naps is universally better or worse than just night sleep. Individual differences are probably swamping any attempt to make sweeping declarations. Personally I do a lot of "just listen to my body" here and over the years and various growth and health stages I've swung all around on what I seem to need.