This coffee shop has a nice vibe and it provides somewhere to go in Lowertown, which is otherwise devoid of business.
That said, it's a pretty generic independent coffee shop: mysterious, potentially un-vegan soup; a few bland sandwiches with potentially un-vegan bread; and mediocre chai. They also offer hummus and tabouli for a whopping $7.25.
The chai comes in a small cup and costs a pricey $3.27 with tax (you could get twice the chai, and much higher quality taste, at Namaste Cafe, or even Caribou). It's a pre-made mix from a plastic jug, with is pretty lame, as I think independent coffee shops should earn their chops by making, say, their own chai recipe or their own proprietary drink/food (of whatever kind). Just because you're independent doesn't mean you should stoop to the lowest level and just serve packaged goods (at a steep mark-up from wholesale rates) that your food distributor happens to offer (which is the case with most places).
Why not have some mockmeat sandwiches? How about baking your own bread or vegan cookies? Anything? Black Dog doesn't do anything to stand out, other than happening to be the only coffee shop in an otherwise empty area. Go the extra inch, Black Dog, and make some food that requires more skill than unscrewing a cap or tearing open a plastic bag.