I finally took the plunge and bought a late 2015 27" imac retina: i7 512GB SSD 8GB 4GB AMD 395X Arrived last week. Haven't had much time to set it up but I initially changed the displayed settings to 'large type'. All fine until I decided to go back to retina settings. Now when I log on and press enter for the briefest of moments the wallpaper takes up a sixth of the screen and is surrounded a thick black border before reverting to the right size. Go back to large type and everything transitions smoothly. Apple Support have done a few bits with me - the wallpaper now takes up a third of the screen before sorting itself out - and their latest advice means I'm currently reinstalling El Capitan. Failing that they suggest lugging it to my nearest store 25 miles away to get them to look at it. Does anyone else have this issue or am I being picky? Having spent a lot of money I considering returning it and getting a replacement as I'm concerned it's graphics card related. Advice appreciated, thank you.