I believe as long as you order something (coffee, desert, cocktail)the deck is available. If you haven't experienced it before you will probably enjoy it.
I know many people were upset with the new rules, but as it had gotten soooo popular it was a complete nightmare. Outside of possible safety concerns, it was just miserable - so many people you couldn't move - it took us about 30 minutes just to get on an elevator back down. Having dined at CG many times and paying a nice price for it I can only imagine how upset I would be as a patron. You could not move anywhere in the entry area because of the people!