My wife and I have been coming to this restaurant for well over two years, and we have not once been disappointed.
The food is fantastic.  It is now the *ONLY* place in the city where we order Mussels (Poulette is my favorite!).  Also try the Pork Tenderloin  superb! 
The service is just as impressive.  Staff remains pretty much the same over the years, and the waiters are very knowledgeable and courteous.  Do make a reservation because this place does get busy for dinner!
As far as ambience goes, Jubilee is simple but very cozy.  Its certainly romantic enough, but has none of the stuffiness prevalent in some of the other French restaurants.
NOTE: check out the new 51st Street location!  Similar menu, same quality, but easier to make a reservation on short notice.  This place is head & shoulders above most other restaurant in the area!
Pros:  Fantastic Food, Good Service, Cozy
                        
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