German Shepherd's are just like any other dog- treat them well, and they'll be excellent pets. Abuse them, and you're asking for trouble. If you acquire one as a puppy, be sure it's from a careful breeder. If possible, meet the parents. The offspring of friendly Shepherd is less likely to be aggressive.
Be sure to carefully train your puppy, as they do grow up to be strong dogs. Training classes won't hurt either. They may cost a small fortune, but it's much better to pay that than a lawsuit in the future.
Keep in mind that these dogs can be domineering, so you MUST establish yourself as 'the pack leader' from the start. Be firm, but don't abuse them. If you are a weak-willed person with no self confidence or intend on leaving the dog to it's own devices, you have no business whatsoever with this breed.
In spite of everything, these dogs are fiercely devoted to their master's, and more than a few have sacrificed themselves to protect them (of course, this branches off of how well you treat them.).
Working with dogs since I could walk.