i've found that it can vary widely in general.  for instance, i found i had to change my monitor's settings after i listened to several people complain about the darkness of an image that showed up just fine on my monitor.  and calibrating doesn't really solve anything if you publish to the Web, since you can't count on your viewers to do it.  i wish there were some sort of standard to adhere to.  i know with CRTs, tv's had a small piece in place ( i think one resistor) to normalize gamma but computer monitors didn't.  now things are even more uncertain and often frustrating. 

that said, i'm glad display technologies are developing as quickly as they are.  and while it's more difficult to control the appearance of anything published online, it's a whole lot more immediate and cheaper than print.  and in my experience, printers can vary a great deal.  color calibration is just difficult.