yep i have 2, scout who will be 4 in april. i got her from a breeder when she was 8 weeks old. salty is 10 and i got her 2 years ago as a foster dog for the NASRN. i however think she has surpassed foster status and has become ours permanently. not officially ours, but it doesnt seem anyone out there is looking to adopt a dog of her age =( which is just fine by me because we love her and i think it would be very hard to let her go to another home at this point.
they are a lot like afewgoodmen described his tibetan mastiffs. they are a very protective breed, but not aggressive. they will try every means possible to deter a threat to their family or flock before they go into a full attack. due to their formidable size, most often a growl or bark is enough to deter anyone. they are typically very aloof with people they do not know. once they know you however, they are huge lapdogs. they lavish affection on their terms, much like a cat. they can never be trusted off lead. they were bred to be very independent thinkers and make decisions for themselves, therefore your commands are not always a high priority for them. they are extremely intelligent and learn things very quickly. they have quite the sense of humor and sometimes if you don't laugh at what they do, you will pull your hair out lol.
they are extremely athletic, and can easily jump fences so a minimum of a 6 foot fence is required to keep them from roaming the neighborhood. scout loves any and all other animals. i made sure raising her that every experience she had with other dogs was a positive one. so she is friendly to all animals. salty on the other hand is very dog and other animal aggressive. it was difficult at first to get her used to a multiple animal household because of that, but we succeeded.
socialization is very important with them. protection training is heavily discouraged.