Well it's a big step for them, Hawaii vs Maxwell was much much worse.
As for performance:
Power usage for Asus 480 is onpar with custom 1060. Performance is single digit % different. Pretty close and these guys didn't include the other DX12 titles.
Guess what happens when they throw in a few more DX12 titles in their benchmark suite? We'll see it in a few months.
Looks like the first Red Devil RX480 review is out.
https://www.computerbase.de/2016-07/powercolor-radeon-rx-480-red-devil-test/
Interesting numbers, very good balanced card and they made the silent bios almost as 1060 power consumption. Of course not at the same performance.