Why would I want to try to get it right in the middle of taking photos, on a 3" screen, when I can wait until I've finished shooting, upload the photos onto the computer, make a back up copy, and then edit them (nondestructively) on a 19" colour calibrated monitor?

Guess what I voted?

Having said that I can see that some people will not want to play around on the computer and can imagine that they would appreciate as much as possible being done in camera before they take their SD card into the local print booth.

(edit to correct a typo)