This is a lens adaptor, not a mirror box. Its needed to be able to adapt A lenses to a E mount body, and still get autofocus and exposure control.
Canon makes a EF to M adaptor, but you don't need a mirror in order to get AF and Exposure control because it was planned on in advance.
But the ad claims that phase detect AF Will be available on the NEX. Does the EOS-M do that with the adaptor?
1DX, 5D3, 600D, RX100
16-35L, 24-70L II, 70-200L II, 100-400L II, 50L, 85L II, 135L, 17TSE, 24TSE, 40, 100 macro, 18-55 II, 55-250 II, 1.4x III, 2x III, 600RT x 4
When it comes to gear, it is better to vote with your wallet. Bitching on online forums like a lunatic doesn't get you anywhere!