My wife and I visited La Lucciola on a tip from a fellow traveler, and were not disappointed. High quality Italian food (far beyond what we expected in Indonesia! Highly recommend the barramundi), reasonably priced (mains for $15-20 USD, cocktails for $11), and the setting was the icing on the cake (right on the beach, perfect view of the sunset over the water, somewhat removed from the crowds of the area). We enjoyed our time so much the first time that we found ourselves stopping in again to watch the sunset after a day strolling the streets in Seminyak.
Highly recommend it for a date night out in Seminyak.