I'm not yet fully convinced. The Deutsch/Wallace exposition is pretty convincing, but when I step back and ask, "Why should there be any probability (in the colloquial sense) at all in deterministic evolution?" The answer seems to defy common sense and I don't know if there is some subtle error.Is Deutsch's explanation fully conclusive?
Incidentally, there is a paper on an attempt at a modal interpretation in which quantum mechanics is really just coarse graining. In this approach, quantum mechanics is not complete, and breaks down at the smallest scales.
The Emergent Copenhagen Interpretation of Quantum Mechanics
Timothy J. Hollowood
2013 J. Phys. A: Math. Theor. 46 325302