The M6 feels a bit lighter than the M3, and I suspect that there is more plastic in the newer body, especially the top and bottom plates, which I think were metal on the M3

Yes, bright light shots are now almost as sharp as the 6D and to the point that you can almost see the mosquitos on the branch that are barely visible before cropping.2

Okay in fantastic lighting conditions

Basically it's a sharp lovely small APSC under bright light, with buttons placement like a dream, without the "wow" factors from the 6D or 5Ds

In good light you get that great Canon color that a lot of people love

The 15-45 does a decent job in well lit in-door situations.