Care to make rigorous how other interpretations require FTL signaling? For that matter, can you actually rigorously explain what it means for worlds to "branch", or why Born probabilities should be interpreted as though they are probabilities in MWI? Saying "all the possibilities actually happen!" doesn't really explain the correlations we actually observe in any interesting way.
You make some good points. Regarding the Born probabilities, the extrapolation of Schroedinger equation to the whole universe seems to make the concept of probability superfluous and the Born rules lose their sense.
