I got my refurbished entry level 2012 15" rMBP in June and I've loved it so far, it's so powerful and the screen is amazing. However, I consider myself a hobbiest photographer and so use Lightroom 5 to process all of my photographs. I've been doing some heavy editing recently in Lightroom and started to notice my laptop slowing down. It mainly shows, for anyone familiar with Lightroom, when I do local adjustments on images. I can paint over an area and it take 2-3 seconds to catch up and re-render the image. Then sometimes when I'm just scrolling through images, photos will render as a mass of massive, pixelated squares which aren't fixed until I force the photo to re-render but zooming into it e.t.c. I presumed the issue was related to RAM as I only have 8GB so I installed a RAM cleaner which has a built in monitor. Whilst using Lighroom and doing these sort of tasks, my available RAM drops to between 2GB and 1GB, occasionally dropping below 1000mb. I presume this means you don't have to run out of RAM entirely for your computer to start struggling - presumably because it can't request enough RAM. I'm turning to MacRumors for confirmation that this is a RAM issue, which I obviously can't physically do anything about with a rMBP but if there's something I can do to alleviate the issues I'm having.