The Restaurant was Great!
We only ate breakfast in their restaurant, so this evaluation is limited.
Furthermore, as a precursor to any travel plans and expenditures in Nantucket, one has to advise that things are very [exploitively?] expensive in this resort area. From my observation, it seems that meals are at least $10 to twice what they cost on the mainland and hotel accomodations easily double unless you have a special discounting deal. My observation, too, is that things such as clothes, jewelery and other general faire (ice cream cones, bikes, small gifts or necessities) are wildly inflated over their comparable prices on the mainland. So let the chooser of vacation destinations beware!
That being said, we had several very enjoyable breakfasts at Jarred's and were served promptly and courteously by an abundance of Russian servers (all with impecable English). For the price, the meal was an excellent bargain. I would definitely breakfast here again and dine if I had more time.