Just an avarage coffee. This goes specifically to their espresso which the taste cannot be covered by other topping, milk & ...
Have been there couple of times, and found out sign of sourness in espresso shots, either the beans havent been degassed properly. or the esspresso is not pulled as longer as requires. Signs of under extraction, maybe. Anyway, its a kindo pitty when they have such an equiped roasting factory behind the store but the esspresso comes out the average. Try their Cortado, its very good.. the milk microfoam covers the sourness and you can enjoy a tick taste of coffee and milk.