I started coming to Adda since its opening last year, and have visited multiple times per week ever since. It's my go-to place to get some work done, since it's usually pretty quiet during the weekdays and has really good WiFi. Their drip coffee is *the best* in Pittsburgh - I've been to all the coffee shops around Pittsburgh and this is not a misrepresentation. The baristas are all very nice and good at what they do, and would eventually remember who you are if you are a frequent customer.
Adda gets quite busy during the weekends, so if you are looking for a spot to get work done over the weekend, you might want to head there early or go somewhere else. Otherwise, it's the perfect neighborhood coffee shop with the best cup of coffee in town.
Other notes: try the quiche and the scones (with clotted cream)! They're nice little snacks that are quite filling.