I own a Macbook Pro with Retina display. Assuming I'm only interested in displaying photos on the screen, is the Retina display calibrated well enough for colors? If not, which method would you recommend to use?
This is not really a bad question if you aren't already well versed in color management. After all, the Retina display is hyped as a pretty fantastic, beats-the-pants-off-of-everything-else display.
But if all you want to do is look at the pictures on the screen, then you only need to use your own judgement whether you like it or not.
But if you are going to reproduce images as prints, then you are concerned about color management. Any display you use for color management should be calibrated. And it should be calibrated periodically to account for aging and other changes. This includes Retina displays.
You also need to follow other detailed (but easy to implement) color management processes to get what you see on your screen to match what you see in your reproductions.