[Rover]

But you do not just get "improved IQ" just by using an FF sensor. If you do all things similar, you end up with pretty much the same "IQ".

The same DOF control then can be had at APS-C too, that was my point. And of course, with adapters you can get other lenses to mount. My post was not about that. And I do not need an adapter on the 6D to mount EOS lenses.... 

Right, but the system is bound to expand. After all, I think nobody expected Sony to start with a 50/1.2 right off the bat, since it's not a high volume lens like a 50/1.8 (there are <i>nuances</i> in this case, of course, as the 55/1.8 is to cost $1000). Secondly, even with the adapter, this is going to be smaller than a 6D and you can adapt lots of stuff the 6D is no good for. SO as a starter, it looks very good. If I'd been starting from scratch a few months from now, I'd get the 24-70 and the 70-200. Going wider would've been trickier but a 10-18 in crop mode looks like a valid stopgap for now.