Retina display is by far the best feature on MacBook Pros. The hardware has 3360×2100 pixels (13″ model) but Apple System Preferences app won’t let you reach that high.
Included there is a command line tool for advanced usage and the simple SwitchResolution app to let you access the highest resolutions of your screen in one click.
I have found that I prefer highest resolutions when working with many windows and lower resolutions when simply reading text. So switching will be even easier if you keep SwitchResolution on your dock.