For many years Lineage was our go-to date night place even though we live nowhere near there. It struck us as the perfect balance (for us) of a little elegant, a little special occasion, staffed with super friendly people, with really good food and drinks, but at a manageable price point. We loved the occasional special like their 1/2 price wine months, etc. The only thing that could have made it even better would have been more vegetarian options (I don't eat meat, poultry, or fish).
What's fitting the bill for others who miss LIneage? We're north of Boston but Cambridge and Somerville work, too. Brookline was truly out of the way (though is Lineage II opened there we would be back!).
For additional information, Highland Kitchen is out other most frequent date night (and family night) spot but is obviously missing the "special/elegant" feel (and the get there by 5:30 or be prepared to wait adds to the angst).