I've read a fair amount about the "Many Worlds" hypothesis, and to me it just lacks in some big ways. I am not aware (correct me if I'm wrong) of any known way to falsify such a theory, and if a theory cannot be falsified, it really cannot be called "science". Philosophy, certainly. But not science. The other issue that concerns me with this hypothesis is a lack of testable predictions (again, correct me if I'm wrong). For a theory to, so to speak, add value to science, it must make meaningfully testable predictions in the real world that extend our base of knowledge in one or more subject areas. All of the big ones have done this very thing (relativity, quantum theory, gravity, etc.), but the Many Worlds hypothesis seems like something more akin to the musings of my 6 year old than it does real science. Obviously, if the theory allowed for meaningful falsification (not saying that it IS false, just that there are ways we could prove it false if it were in fact false), and could offer testable predictions that are within our grasp within the next 500 years, then I think I would be more comfortable with the theory of Many Worlds.