In many cases a home owner's insurance company will
attempt to drop you for owning what they deem a "dangerous" breed of dog, even if the dog has never bitten anyone and/or you are a long standing customer.
The American Kennel Club (www.akc.org) suggests people who own such breeds have their dog complete a "Good Citizen" program or something equivilant.
Hounds Town University offers a complete temperment evaluation for this exact purpose. Michael Gould will evaluate your dog with humans and other dogs in a variety of situations. He will then provide a letter certifying the dog's temperment and his observations.
It's recommended this evaluation be done every year as a dog's personality can change over time. The fee for this is $200 and is done on-site at Hounds Town University.