The summer after our first year in graduate school I shared an apartment with a classmate a block away from Delfina (and its excellent neighbor, the Bi-Rite grocery, but that's another review). They were still a brand-new neighborhood restaurant then, and the personal warmth and excitement of the owners came through in everything - from the thoughtful design of the interior space, to the attitudes of the hostesses, servers and bartenders, to (most especially) the food.
Unlike some of it's local peers, Delfina's strength isn't 'fancy' or elaborate preparations, but the (to my mind) more difficult challenge of executing simple dishes with incredible care and attention to detail. Even in a simple dish like white beans, the ingredients are superb, the balance of flavors delicate and precise.
There aren't many Bay Area restaurants that I miss, but Delfina is one of them. I know it won't ever be the same little neighborhood secret that it was that first summer, but it still has a place in my heart.