Very confusing post! Is it about OBC or gift cards? Or BOTH? T&C on a Gift Certificate (I'm copying directly off one) says, "can ONLY be used for new bookings, not to be used to settle any ship board charges".
We're just off a week on Allure. The non-smoking casino was deserted the times I went by. That said, the smoke level/smell in the regular casino was never offensive.
I'm just off Allure, and personally can discern no difference from her mattresses and any Celebrity ship (Apex, Solstice, Reflection, Silhouette) I've been on. Just from a logistical standpoint, I can't imagine there would be any substantive variation fleetwide between ships/brands.