Yes. The upper level of the dining room is assigned seating and the lower level is AYWD (As you Wish Dining). You have to make a reservation each morning if you want AYWD.
If you have assigned seating, you cannot go there one night, then to the AYWD another night and so on. You have to choose either one. We always take assigned seating but I think this is the way AYWD works. Someone please correct me if I am wrong.
You can also eat dinner in the Lido between certain hours or eat in the Pinnacle Grille - cost there is $20.00 pp for dinner.