Just got my first casino offer after playing for about 5 hours in the casino and getting about 650 points, I'm mostly a video poker player so it takes me longer. I ended up losing about $200, and the offer I got was 40% off the casino rate and drinks on us while in the casino on my next cruise. Booking an interior on the Liberty in October as an example would be about $500 with the taxes and fees included, plus the drinks for a 3 day weekend cruise.
Given that I can split the cost with a friend, I can essentially cruise for $250 for the weekend, and he gets a good deal.
Taking into account this is probably a savings of about $100 over normal rates, and then the added drinks, if I drink more than 10 drinks on the cruise for free, it's essentially even. (Not counting what I lose the next time, but then who knows, more offers I guess).