I have one, called Bear, he'll be 3 in august, all I can say he's totally different from any of your normal breeds of dog, no matter how much experience you have with other breeds they are just so different! They are far far more independent for starters, not food orientated at all so forget trying to use treats or praise as a motivator, very strong willed and will only do something if he deems it neccesary or in the intrest of the saftey of his family so forget a breed that will want to go for long walks, do obedience and play fetch!! It took us ages to get what I would call basics with a normal dog and even then you can see he's not really intrested as it has nothing to do with what his instincts tell him - they were bred to be totally independant of people, Bears recall is only if he wants to, sit is an occasional thing, he learnt very quickly how to get out of doing something he doesn't want - we shut him in a stable when we have visitors who don't like dogs etc - he rolls over on his back and acts as a dead weight now and even draging him is not an option at around 8 stone, he's getting better but he has had to be put in a stallion stable as he's eaten his way through one stable door and a kennel door too!!!
I would not have one as a pet, they are a working breed full stop, we used to keep Bear indoors up until he was about 6 months old, he put his head through 2 windows trying to bark at the postman so he then moved outside, he also couldn't cope with the heat indoors even though we have stone floors and no heating, he didn't like not being able to see around him either! Their guarding instinct is very strong, Bear sat outside my bedroom door from 12 weeks old onwards as he could see all of our yard, he didn't move all night!! He now roams our 12 acres 24/7 and does as he pleases, most of the day he spends sitting on the front steps or in the middle of the yard to watch the gate even if it's blowing a gale and pouring rain he doesn't seem to notice, at night that's when he's at his most active he patrols the fields and woofs at most things - so not a dog to have if you have neighbors as they are very loud!!
They're not the sort of dog that will really play with others, we have 3 ridgebacks and 2 terriers and Bear likes to play with one of the terriers as he grew up with her although his idea of play is to pick her up by the tail and fling her or sit on her if she starts to yap at him!, he does occasionally chase a ball a few feet and wander off with it, he has a collection pile of things he's found, he's very good at finding lost horse shoes in the mud, so a bonus there!
I know someone else locally who has one and his is very much the same, he actually bit a delivery guy though as he made a sudden move towards the guys wife over their gate with the thing that you sign on, so you need to be very aware of what they are upto which can be hard as their body language isn't quite the same as other dogs and they don't give much away with their facial expressions either - think large fluffy rabbit that looks half asleep!
You need 6 foot fences too really or certainly higher than normal as they can jump and I'd say they probably would if needs be, so think very carefully before you get one, where abouts are you as you're welcome to come and meet ours, there are a few other CS owners about so well worth meeting a few before you buy and make sure you find a good breeder - there are only a few breeders who breed in the UK thank goodness so you may have to import.