I’m using KiCad 4.0.6 on OS X 10.9.5 on a non-retina MacBook Pro, and I haven’t noticed any performance problems. KiCad seems quick and responsive to me. (I have 16 GB RAM, and an SSD.)
That said, there are some issues. Templates don’t work on OS X. Control-click to right-click doesn’t work in OpenGL mode. The binding for the trackpad is counterintuitive (I’d much rather have two-fingers to scroll and pinch-to-zoom.) And I’m always encountering minor little bugs that made KiCad seem unpolished. Since I haven’t used KiCad on any other platform, I don’t know how many of these bugs are OS X specific, and how many are KiCad in general.
But with an external mouse, KiCad seems quite usable on OS X for me, even though it isn’t perfect.