Stayed at the Monte Carlo this week, RC offer with $100 resort credit. I came in late (11pm) and was told at check-in the resort credit applied for any MGM properties.
The next day I went by the Mlife (Gold/PLT/Noir) check-in just to double check and they said no, only Monte Carlo charges apply. Was able to eat/drink at The Pub, Double Barrel, Boulevard Creamery and the buffet with my credit. FYI, taxes are included but tips are not.
Was my first time using this offer, adding the resort fee, if you can get in on weekdays when room rates are sub $40, I think this can be a good deal for hotels with 100-150$ credit.
For the Aria and its $200 credit, I may even consider it with those $98-101 room rates. Just because I have never stayed there and want to try its facilities/restaurants.