 Vaidman 2001 finds it advantageous to think about all worlds together even in analysing a controversial issue of classical probability theory, the  Sleeping Beauty problem.  Accepting the Probability Postulate reduces the analysis of probability to a calculation of the measures of existence of various worlds. Note, however, that the Quantum Sleeping Beauty problem also became a topic of a hot controversy: Lewis 2007, Papineau and Durà-Vilà 2009, Groisman et al. 2013, Bradley 2011, Wilson 2014, Schwarz 2015.