Does anyone else have this issue since upgrading to Yosemite or just me?
Controlling the brightness and/or volume by pressing the equivalent keys (i.e. f5,f6,f11,f12) isn't instant like it used to be in Mavericks and before that.
On startup they're as responsive as ever, but as time goes on (i.e. two or three hours of working) I'm getting more and more lag on the brightness/volume controls to the point at which they just stop responding.
This is on a 2014 rMBP (i7/16GB/1TB SSD) connected to 2 x Thunderbolt displays