I am interested in starting my own local pizza restaurant. I would estimate how much sales they are doing by discreetly asking employees, suppliers and video taping incoming food orders and computing that info back to sales. I might also plant myself across the street on a Friday night with a clipboard and count cars, deliveries etc. This would give me a rough indication of how successful they are and if I could and want to compete with them. This is the Papa John's theory.
Dining rooms are great if they are always used.
They really raise the cost of operations because they are fairly non-productive areas that you have to heat, cool, pay taxes on, clean and maintain. If you don't have to have one I wouldn't do it at this time. Big monster to manage. If I had to do it over again I'd find a building with 1300-1500 sq. The best POS system in my opinion is RapidFire.