I think monochrome in camera really pays off if you know that you're gonna have to do a whole 'themed' shoot in monochrome or sepia... in that case it would be more time-consuming to do it all in postwork. So, I guess the monochrome in-camera has its purposes... But for casual shots, I would always choose postwork.

We do not see things as they are. ǝɹɐ ǝʍ sɐ sƃuıɥʇ ǝǝs ǝʍ