Essential for Jpeg shooters and for those who converts RAW files without any post processing using default camera manufacturer provided software.

Nikon users, please turn off Active D-Lighting when shooting sun in sunrise/sunset shots as it may create a strange color bands/shadow around the sun as in the picture http://indianaturewatch.net/displayimage.php?id=130361

Canon and other camera users can also check the same with the similar feature on their cameras (Highlight tone priority/Auto Lighting Optimizer etc)