There are 2 locations. On Long Island's South Shore, it's in Rockville Center and in the Mid-Island, it's in Jericho. The food, service and ambience are outstanding. Pricey, but you get what you pay for.

I know Long Island quite well. If you give me an idea of what type of food you're looking for I'll be happy to throw out some recommendations. Also, as Long Island is around a hundred miles long.... we might also have better luck if you could specify general location. Nassau or Suffolk County at the least. There are a few great restaurants through Nassau and Suffolk both, but they have hefty drives in between them...

In Buffalo, "FIDDLEHEADS" is great. If we are there 4 days we would dine there twice. Good price, GREAT food. Greenwich Village feeling. Go up Deleware Ave. Right onto Allen just after Holiday Inn. Go about two blocks. On corner on right.        http://www.zagat.com/r/fiddle-heads-restaurant-buffalo                      If you get time let me know how you make out.

As a rule the close you get to Manhattan the more choices you have but the more pricy the food becomes.  Not an absolute, but somewhat true.  If you decided the Nassau area, like Westbury there's City Cellar, Toko for sushi, West End Cafe, Seasons 52 for healthy grilled food.  If you are staying in the rt 110 area then Huntington has some nice ones.  Up there Prime is good and it is right on the water,  Ariiana is interesting.  Lots of choices, try Zagats online guide.   Remember long island has a lot of families, so the restaurants may have good food but the atmosphere may not be all that fun.

Best Italian L.I. and better than most in the city....

Casa Rustica in Smithtown and Mario restaurant in Hauppauge.