They add interest and often times, they bring a premium on eBay. Some, however, consider them to be a flaw or distraction, so they avoid them altogether. Depending on the coin, the die crack can make it famous! Such as this 1807 "Bearded Goddess." (image from PCGS CoinFacts). You will find some good information here: http://www.cointalk.com/threads/is-this-true.238890/
Your 83-CC is not special because of the die cracks. Keep in mind that it required 130-150 tons of pressure to strike the coins, so die failures were pretty common. Chris
speaking of die cracks, is it possible for a counterfeiter to put in a die crack and maybe die rust mark, as described on a famous coin?
Yes, but it will be possible to tell the difference unless it's copied from an original via high end transfer die.