I've read multiple accounts of people who tried it and claimed they were just as rested. But I emphasize try because they no longer do it, and I bet the reason is they were not just as rested.
There was that guy (though I cannot remember who it was) who claimed to have sustained polyphasic sleep for 9 months and only stopped it because he found it hard to interact with people and socialise because his schedule was too different from everyone elses. But, I have no evidence, so.. that FAQ seems reasonable though.
edit: polyphasic sleep discussion: http://news.ycombinator.com/item?id=652650