Postulates that the observer obeys different physical laws than the non-observer, which is a return to vitalism. The definition of an observer varies from one adherent to another, if present at all. The status of the wavefunction is also ambiguous. If the wavefunction is real the theory is non-local (not fatal, but unpleasant). If the wavefunction is not real then the theory supplies no model of reality.
http://www.hedweb.com/everett/everett.htm#problems