We managed to go on 3 cruises last year with casinos at sea and upgraded at the last minute to Havens on 2 of them (before they started the bidding process). You will also get some treats delivered to your room from the casino. You will still have to pay the service fee for the promos. You will get free drinks in the casino which include bottled water (not included in the beverage package).
So we have always gotten the free drinks and specialty dining. We have always paid for an upgrade to a balcony (usually comped an inside room). Yes you will get the perks with your booking just like you would a regular room.
