Not good. Either the bread is too dense to start with (maybe it is a French baguette and not a Vietnamese one?) or it just sits around getting stale all day with butter on it. The coriander is mostly stems. The only redeeming quality of this place is that the tofu-mushroom mixture on the vegetarian sandwich is fairly tasty.
I agree, go to the place across the street, or throw "authenticity" out the window and go to Vua in the Quartier Latin which is really good. It's obvious when you see the sizes of the respective crowds which place in Chinatown is better...