I went to Market Street Catch on a whim tonight after the gym, and I was surprised by the quality of their fresh fish (and I'm a native New Englander from the coast). From the outside, Market Street Catch looks like a typical bodega/quicky-cafe, and that seems to be the ambiance on the inside. But service was good, the prices were better, and food arrived rapidly: so that was enough to impress me. There is a decent variety of fresh fish - I went for the grilled salmon with salad - and the portion size was ample. Just a main was enough to fill me up. The only place I'd knock Market Street Catch down a point was that the decor was a bit too fast-foody, but then they wouldn't be able to offer these prices if it was more upmarket.
I'd definitely recommend Market Street Catch if you are looking for a quick seafood meal that isn't pre-prepared.