Our line has one Airbus fleet that is FLS equipped. We only have one non-ILS approach in the route system that does not allow FLS, which is trained specifically in the simulator. For that fleet, FLS does dramatically simplify the process of approach preparation and execution. The only disadvantage would be the inability to use FINAL APP to perform RNP approaches, as previous posters have mentioned. From what I understand an upcoming MMR upgrade will eliminate that limitation.