If you get to the pier and find that you are upgraded to a Cat 11 or 12, or if you were smart enough to book this on your own, you can use the Skipper's Club to expedite boarding. It simply allows you to skip the long lines. Just ask for it like crazy after you pass through terminal security but before you get into long lines. They don't volunteer the information, though, so be assertive. We used the pre-cruise check-in at Sheraton Biscayne Bay, however, and understand there are no further time savings if you do that.
You receive a repeat cruiser invitation in your cabin the day of the repeat cruiser party. This was our first cruise when we should have been invited to this party. Our travel agent put our past guest number on our booking, and we made certain to check the box on our boarding pass that we had cruised Carnival before. On the ship we made fast friends with another couple who had sailed Carnival 7 times. So, we agreed to let each other know when the invitation arrived. Sure enough, they got one, we did not ... so we went to the information desk and were immediately issued the invitation. Since this information doesn't make it in the Capers or posted anywhere else, we would not have known if we hadn't taken extra precautions with our friends. And, it was worth it ... great drinks, appetizers, desserts, music and dancing ... without having to dress up. Carnival through a great past guest party!