We have sailed Carnival 16-18 times and have a Carnival cruise coming up in a few days.
We like the platinum perks, especially the priority embarkation and disembarkation. Getting off early is a big help when you drive to the port. You can be in the car and away while most are still milling around.
We have sailed the other major lines and like them too but really dollar for dollar and pound for pound, Carnival can't be beat.
Happy sails to you.