As much as I like to think I know my camera backward illuminated buttons would be a help at times. It wouldn't be a big selling point but its definitely very useful.You are better than me then. I do use a very compact travel tripod so I'm regularly shooting from 12"-18" above the ground so even though the buttons might be in the same place relative to each other they are not in the same place relative to me. I also regularly use and adjust lights for dawn shots so walk to and from the camera a lot of times in the dark. But I'll often use a CamRanger or WFT in situations like this so I don't have to keep bending down to adjust the camera and I can do test shots from the light position rather than the camera position.
Bottom line, I would find illuminated buttons useful, other companies offer them. You wouldn't, that is fine.
Here is an example of when I'd find them useful, pre dawn shoot, seven lights, setup in complete darkness.
I'll be interested in what they do about keeping the camera silent when required. I think it will get more common that people will expect press conferences to have the noise of cameras kept down. Same for weddings and some sporting events. Now that's its possible to be silent , more rules may come into play. Yes you can flip the mirror up but unless the viewfinder is some sort of hybrid its not ideal. It will be interesting if they try to solve that issue. None of the Canon DSLR's are particulary quiet on silent mode. A hybrid viewfinder would be attractive to me.
The key selling points for me will be the progress in focusing, ISO performance and FPS.
I'd be surprised if they don't move the MP slightly at least as it nudges people to replace their 1 DX II's.
You'd need a significant improvement in focusing and ISO performance otherwise as a 1DX II is very robust and would work on for most needs.