So I picked up a base model iMac Retina. Everything was silky smooth until I hooked my other 1440p monitor up. Now mission control is pretty laggy. Remove the extra 1440p and everything is perfect again. I would like to see someone test it out on the upgraded video card. I use mission control a bunch so I would be willing to return the computer and order an upgraded one if it is going to be laggy. uploaded a video of it with and without the extra monitor plugged in: http://youtu.be/S96D3z2JwQg Wasn't as laggy as it sometimes gets in this video, but it shows what I mean. Edit: Another way to test if you have an m295x, but no 1440p monitor, is to open up a bunch of windows and crank the scaling all the way to the top. If I do that on the 290x without the external display hooked up it can get laggy as well.