I would like to address a couple of points. Dress code in all Specialty restaurants including Blu is smart casual every night regardless of the dress code in the Main Dining Room.
The fee is bascially a tip for the personnel in the Specialty restaurant.
The specialty restaurants IMHO are giving you the same service and food as you received in the MDR in the early 90s when Celebrity was renowned for their food.
The nice thing about the specialty restaurants is that it is your choice to go, no one is forcing you.