> Wave collapse feels like nonsense, requires arbitrary notions of "observers".
There's recently been a long thread over on PhysicsForums about the Wiegner's friend experiment. The thread was kicked off by this paper detailing a realization of the experiment, in which the authors conclude "this result lends considerable strength to interpretations of quantum theory already set in an observer-dependent framework and demands for revision of those which are not."
Then again as far as I can see MWI doesn't come out victorious, "one way to accommodate our result is by proclaiming that “facts of the world” can only be established by a privileged observer—e.g., one that would have access to the “global wavefunction” in the many worlds interpretation".
Then again I haven't studied QM so what do I know. Fun to think about while on the bus tho!