I wanted a quick meal on my way to the airport, and stopped by after reading Tripadvisor reviews. The food area is located in the back corner of the store full of various kitchen gadgets, and there's no room to sit down and eat within the store...it's all take out. However, there are lots of benches on neighboring streets, and a park just a block away.
I ordered a BLT on ciabatta bread, and it was easily the best BLT I've ever had. The sandwich came with chips, and was $10. It is probably the priciest BLT I've ever had, too, but it was worth it! Relative to the cost of other meals on the island, it was a good deal. :)
They offer meats, cheeses, and other sandwich fixings on various fresh breads so you can make whatever kind of sandwich you'd like. They also offer several different salads and soups, though on the day I came they were out of soup.
Not only did they make a great sandwich, the owner (?) allowed me to charge my dying cell phone in the store so that I would have my GPS to make it back to the airport for my flight.
If you're looking for a quick, fresh, and satisfying lunch, Nantucket Gourmet is a great option!