I just upgraded from my Core i7 2012 iMac to a Core i7 4.0 Retina iMac a few weeks back. I clean installed Yosemite 10.10.5 on my 128GB SSD, while keeping my Home folder ont he 7200 RPM HDD. I also upped the RAM to 24GB. The Vid card is R290x. Problem is that the animations/transitions in UI elements on my machine feel a bit sluggish. Mostly switching windows, or while switching desktops, I notice a low frame rate, which surprises me because the machine is no slouch. Any ideas what could be causing this, or should I take it in to be checked out?