When we made platinum, just about the only real perk was the meal at Palo (more so as they keep raising the price). But another good one for us is the #1 boarding number. We show up early enough (9:30 or so) to enjoy the crowd anticipation in the terminal...
....but for us the best part is going to Cabanas and getting a window table. We just love having Cabanas all to ourselves (or so it seems for about 15 minutes), and watching the port life from our table. We get to interact with our first crew members, as the waiters there aren't yet incredibly busy as they will be after a while. Every one of them has an interesting story, and it's fun to find out where they're from and what their family is like. It's a relaxing lunch, and we feel the ship come to life.
The timing is good, by the time we are finished the room is filling, so we are able to move on to let others enjoy the setting. We still enjoy watching the port life, so we'll find seats near the outside of the ship (on the newer ships usually near the coffee shop) and again it's fairly quiet and the view is wonderful. We know the ships, we already have our Palo reservations, so we don't have anywhere we need to go. We wait for the room access time to arrive, unpack, go to the drill, then the bustle starts with the sail away party.
Relaxing, invigorating, and transitions from the shore life to the leisure at sea.