F3G
Mine is clearly just a residence permit, being labelled 'Titre de Séjour Spécial' and is issued by the Ministère des Affaires Etrangéres though it does look like an ID and I do use it as such. The only place where I've had a problem with border crossings is Switzerland, obviously most of them speak French so they know what it is.
I have asked about a national ID card and the answer has been along the lines of - you're an EU national and it's up to your own government to issue an ID card, you have a residence permit and this is to be used in conjunction with your passport/nationally issued ID card. Though I am married to a Fench national and have lived here for a number of years and could receive French citizenship if I wanted, though as much as I like the French I've no desire to become one of them:-)
Interestingly EU citizens are no longer obliged to obtain residence permits in France (I think the normal one is called a Carte de Séjour, mine being different because it also confirms my diplomatic status) and many do not but it's difficult to exist in France without something official looking issued by the government, for example, without one, you would find it difficult to obtain a loan or mortgage....