At the same time, he found that polyphasic sleep results in poorer performance compared to normal sleepers. And this was considered non-noteworthy, since obviously 2 hours of sleep is worse than 8. You can find his articles on Google Scholar.
Steve Pavlina is the only person I know of who has claimed to be polyphasic for an extended period of time and claimed that there is no performance decrease. Unfortunately, Steve refused to do any scientific testing and relied entirely on his own subjective judgment. He gave it up after 6 months anyway, but still maintains it is effective.
Steve's Pavlina's experience however exactly fits in with the best scientific understanding of sleep (which Wozniak perfectly elucidates). Steve Pavlina was never able to maintain the schedule without an alarm clock, which indicates that his body did not adapt and was not co-operating or behaving in a "natural" way.
The theory that Steve was only getting REM is shot down by his own journals which indicate that he was getting both Delta and REM. My own experience with polyphasic also indicates that while the proportion of REM may increase, you still get delta sleep. I was fully (and rigidly) polyphasic for some weeks but never stopped having delta sleep. I also consistently showed decreased performance that could only be overcome by surges of adrenaline and autonomic excitation in general - which is easily caused when a loud alarm clock wakes you up when your body desperately desires sleep. You are tricking your body into a state of permanent fight or flight.
Anyway the studies were done in the 80s that directly measured performance. But in the modern day extensive studies have been done on sleep and everything we know about sleep now shoots down all the theorizing that the polyphasics use to justify their crazy. The idea that delta wave sleep is useless has been utterly rejected because it has been shown that delta wave sleep contributes to long-term memory encoding. If you cut down on delta wave, you cut down on long-term memory. If you cut down on sleep in general, you cut down on cognitive abilities in general.
This trade off may be worth it for some people, but they should be aware that it is a trade off. Magical thinking like that displayed by Steve Pavlina does not magically make you immune from the negative side effects of sleep deprivation. You get over the drowsiness with sheer strength of will and adrenaline, but the fogginess doesn't go away. (Steve considered the fogginess to be a benefit. But remember this is a guy who believes ghosts tell him how to win at blackjack.)