Hi guys, Just got a replacement due to screen shadowing in my previous RMBP. This screen looks great, no problems, and it's Samsung. However! The computer lags!!! And my previous one didn't have these symptoms. For instance if you go to about this mac, more info, and change the tabs between overview-display-storage-memory it changes the info, but not smooth. I noticed it right away. Or if you for example in system preferences and going to different settings, it is not smooth at all when opening one window and then going back. It is like for a millisecond previous window shows while new one opens, hence the lag. There is no lag in safari though. It looks like only system applications do that. And if you swipe spaces, it does lag as well. It is noticeable especially if you go slow from one space to another. I have not used my previous RMBP and sent it back right away due to screen problem, but I'm sure that kind of lag was not present in my previous machine. I'm gonna go to Apple store to try another machines, but meanwhile could you give me some info on that? Is your smooth as butter on those? And yes I did update everything to latest OS.