I am a developer and have been trying to use my rMBP (specs in attached png) with three external monitors (with the lid closed). The monitors are two Dell 1920x1200 monitors and a Dell 4K monitor scaled to 2560x1440. I was previously using tw0 2560x1440 (one Apple, one HP) monitors and one of the aforesaid 1920x1200 monitors. In both cases I experience drastic degradation of the OS performance. Everything gets really slow - from mission control to web page loading. As soon as I drop back to using just two monitors (doesn't matter which two) then everything seems fine again. I do happen to have a lot of desktops going (~8-10) and often have a lot of application windows open. I was just curious if this behavior is typical. Has anyone experimented and discovered any more specific parameters that make this behavior any better or worse? I really like having the display real estate but not if it is going to send my computer into a stupor. I'm wondering if it would be alright I replaced the two 1920x1200 units with a single 2560x1440 or even a 3440x1440?