Well, you are definitely covered from the time you get your attestation, so I guess if you have sent your request in, it is accepted and no further documents have been requested, you are covered from the date CPAM receives your request. Otherwise it may not be until CPAM receives the additional documents. Of course you could always just keep all your feuilles de soins and submit them anyway and see what they pay.Thanks. So, that brings up the next question... How does one determine that date? (Obviously sometime after they have received the application -- all the more reason to use a lettre suivie or lettre recommandée.) I don't think that date is visible on the Attestation de droits. The date the numéro sécu (permanent or temporary) was issued is also not visible. But, in that case, at least you have the letter they sent.
This is only of academic interest to me. But might be of some importance to ssgray.
Re fees charged by specialists it is wise to check that the specialist is 'conventionné', or once you have a mutuelle (once you have your attestation) has an agreement with the mutuelle in relation to fees.