...I'd go so far as to say worst Mac we've owned ever... A while back we bought new from Apple a late 2015, 27-inch, Retina 5K iMac. (3.2GHz i5, 16GB RAM, AMD Radeon R9) as our new family machine. Now our first Mac was an LC475 (also know as 'that pizza box Mac...') so we've been through quite few different Macs over the years but I have never encountered one so bad as this machine. Just insanely slow & laggy. Everything takes forever to happen with spinning beach balls on everything you try to do. Even right-clicking for a drop-down menu can take 5+seconds for it to appear. I've run all of Apples diagnostics & keep it up-to-date but I'm guessing that this was just a total dog of a model. First off - anyone else had any experience with this model? And second... - anyone have any suggestions for further diagnostics or fixes?