Besides the fact that they have a phenomenal selection of meats & cheeses, they also have some of the most helpful, knowledgable staff around. I've come in on multiple occasions, not at all knowing what I wanted, but knowing I needed to make a cheese & meat platter for six. All I do is tell them that, & they start pulling cheeses & slicing off slivers for me to taste! They're just wonderful at Penn Mac.
PS Try the English Gloucester cheese - it's a rich, orange, sorta cheddary cheese that's chock full of chives! Basically, the ideal cheese for potatoes.