Carnival does offer a lot of advantages for booking a suite. Like you mentioned, you are the first to board the ship, and there are also priority lines for you at places like Guest Services and Carnival Adventures (their shore excursion desk). There is also priority tender disembarkation if your ship sails to a port that a tender is required to get ashore. Unfortunately you won't receive double VIFP (Very Important Fun Person) points for your cruise. I'm also not sure if your room will be cleaned twice. The last cruises I have travelled on, my family got a balcony so I don't know if your room is cleaned twice. I want to say it is, but don't take my word for it. As for the priority dining times, just call Carnival or go to your booking reservation and click for the dining time you want (the options are: 6:00 PM, 8:15 PM, or Your Time Dining [so anytime]). Finally, the onboard credit can be put to many things. It could be used to purchase drinks, food, shore excursions, and various packages (including internet and drinking packages). Hopefully this helps and enjoy your Carnival Cruise!