I don't think there is a best night. It depends on your preference. We booked on a sea day, but that was our preference. If it is a formal night on the ship you must be dressed formal. On all other nights a tie and jacket is perfered for men. No matter what night you choose it is truly a dinning experience. I do recommend the warm goat cheese suffle. Enjoy your cruise. She is a beautiful ship.
Ryan, we went twice during the week: the first formal night - uncrowded and service was prompt and excellent; and then we went the last night of the cruise - over-booked, crowded and service was extremely slow. I think the message got around through the week of what a wonderful, worth-the-money experience it was, and, consequently, everyone wanted to go at the end. So my suggestion is book early and go early in the week.
And I echo Maria's recommendation for the goat cheese souffle.
It is truly worth the money. We did it in February 2000 and wouldn't hesitate to do it again. I recommend the sampler dessert. it was scrumptious! wish they had a specialty restaurant like this on the Galaxy so we could enjoy a meal like that in March.