I am going to buy my first mac, which is 15" base retina model, and I have some questions about it. I will be glad if you help me. 1- How much of the 256 gb capacity will be available when I open my mac first time? 2- I read sonewhere that mac OS uses some of my ssd's capacity when go sleep or ram's memory is full. If this is the case should I extract additional 8gb from the available capacity of my ssd? 3- Does macbook gets slower as available ssd capacity gets reduced? Because that was the case with my iPhone 4. 4- Will I have problems w/o dedicated gpu when watching 1080p or 4K movies? And I am power user, I use applications heavily and simultaneously; like editing several office documents, playing songs on itunes and surfing safari with tons of tabs open and a few more apps running background. But I have nothing to do with gaming and video editing. Is 15" base model enough for everything works fast for next 3-4 years? Thanks a lot.