It seems every new Mac these days have some sort of UI lag or another - from iMac 5Ks to MacBooks. I'm really curious how the 5Ks work on El Capitan. I'm hoping for a really smooth experience. Apple claims that that Metal for OS X "speeds system-level graphics rendering by up to 50 percent". Also - Mission Control no longer seems to have transparency effects. So.... No more Mission Control (or any other UI) lag? Can't wait to see how it works on my iMac 5K, gonna try the public beta in July. If anyone tries a developer beta, tell us your experience regarding performance.