In the terminal there is a
Castaway Club check-in line, but found you can check in at any line. It actually took took longer to check in there than at the regular line. Two weeks ago I just waited in regular lines that had the least amount of people in it.
If you book and sail again within a certain amount of time, the Castaway Club will give you a onboard credit. There is no discount rate for Castaway Club members (though I think there should be). Something like frequent sailing discounts or something.
Onboard there is a special CC club reception with the Captain and senior officers. They have complimentary snacks buffet and drinks (alcoholic and non). It is very nice.
Oh, and I forgot to mention the free gift in the stateroom. We had sailed 4 times with
DCL and the last time we had a black DCL duffle bag and a "crate of snacks" such as soda, chips, pretzels, candy.
MJ