Guess the best idea is if you want to play slots use the mainland casinos since paybacks are generally posted and strictly regulated. Cruise lines in my opinion stick it to the customer a little harder than regular casinos. To add insult to injury they dont even offer a single free drink to the players. ( Another reason to sneak on alcohol).
2008-Valor and Glory
2009-Spirit and Splendor
2010-Freedom of the Seas and Mariner of the Seas
2012-Allure of the Seas and Navigator of the Seas