This location (2nd busiest in Pittsburgh) is one of my favorites, although it can be difficult to A) find a place to park and 2) once you find a parking place, finding a seat inside, and C) getting out of the place. There are parking places in the drive through lane so to exit you might be behind quite a few cars waiting for drink in drive through.
It has all the necessities (2 comfy chairs, plenty of tables, and all the drinks and snacks) in a very tiny space. And, the reason this store is so busy, is the drive through and it's right off the exit of 376.
One of the baristas told me this wasn't built to be a Starbucks, which is why from the outside it doesn't resemble one. It's between Olive Garden and Einstein Bros.
PS the baristas are fab!