FWIW: I've been using Bouygues' prepaid Carte Nomad for six years now (during short vacations and a 14-month stay in Paris with heavy use as well as occasional "roaming" in the US) without a single problem.
Perhaps from a regular subscriber's point of view the service isn't good, but I have no hesitation in recommending their prepaid service.
Glad to hear that.
I am a regular subscriber to Orange and I receive a monthly bill.