Like others I have had a bit of slow-down and lag in the UI on my new MacBook, but the main issue is the way the trackpad feels. It's like there is a small amount of lag between moving my finger(s) on the trackpad and the mouse pointer reacting. Not enough to see, but enough to just feel wrong. Same thing with scrolling up and down. That minuscule delay can be very obvious. It's something I notice using the PC laptops at work but not something I've experienced on a Mac. Switching between my 2011 MBA and the new MacBook there is an obvious difference. On the new machine I feel slightly disconnected from the mouse pointer. On the old machine I feel like I'm moving the pointer with zero delay. Turning off transparency, resetting SMC/PRAM, fixing permissions etc makes no difference. Changing the tracking speed doesn't help either. Anyone else experiencing this? It's driving me crazy(er).