Every locals has an experience with this place. For many it was the final frontier of a adventerous night out on the town. The reason for the attraction is their amazing pizzas. For many, this is the best pizza in downtown Reykjavík.
I wouldn't call this nice dining. Actually there are real tables, just a counter with some chairs on it. Despite these disadvantages it's quite a tasty pizza. It's not trying to hard on the interior, as their main effort goes into creating the perfect pizza.
Best tip I can give you is to take-away the pizza, as the interior is pretty shabby.