FF is about MUCH MORE than "good mouth habits" (which it's great for). It's about the dog learning to work under pressure. The dog learns that he does things NOT ONLY because he likes to, but because it's his job. FF is the foundation for much more advanced training as well.
It provides momentum, it teaches the dog that it has a job, it gives the dog good mouth habits, it enhances all other training that involves "pressure", and it makes a good retriever into a great retriever.