In my opinion the move to mirrorless can result in less parts, less cost, possibly longer life span and a more direct path from image to sensor. It will upset the folk that insist on a view of the image TTL (through the lens) but as processing speeds went up over the years I think mirrorless models with a viewfinder are a really good idea.
I won't miss all the noises that occur when the mirror moves inside the camera. I'm sure you won't either.
Your slow to focus comment is mildly interesting. When we move up from point and shoot models we may want to manually focus. Low light focus speeds are always slower. Not much to discuss here.
I have been looking at a new small camera and like the option of interchangeable lenses, but have some questions.
I now have a Canon 60D DSLR and a Nikon L810 point and shoot.
The 60D is a great camera, but not one I want to lug around somewhere like the crowded shops and trolley cars in San Francisco or the Metro in DC.
The 810 is about the right size and does good on picture quality, but is very slow to focus unless you have lots of time and light. So am looking at a better P&S camera.
I have read a few articles on mirrorless cameras, but still don't understand the advantage over a good P&S with a zoom lens.
Is there any advantage and if so what is it?