so i'm debating between a MBA and a rMBP as my first foray into Apple-land, and I'm a bit perplexed on "retina" and how it relates to resolution... I understand the concept of retina, in that it's meant to prevent the distinguishing of individual pixels. What i don't understand is scaling, "best" resolutions, and how all of that relates to how things look on the screen (aside from just appearing sharper). The MBA native res is 1440x900 and the rMBP native res is 2560x1600. That retina resolution doesn't seem very "usable" on a 13" screen. And I've seen information thrown around about cutting that in half as a useable resolution (which would be lower than the MBA). I guess I'm just really confused. Because as far as I can tell, retina is really just about the lack of visible pixels and not necessarily higher useable screen real estate? Does anyone have a good resource they can point me to? Thanks!