I have known folks who have owned them (and been herded up against a wall firmly but inexorably when said dogs wanted to be petted). I also know people involved in Newfoundland rescue and in raising Akitas, also big dogs with lots of fur who tend to want to be in charge. I currently own an American Bulldog, who at 120 pounds of love is about half the size of my friends’ dogs, but who has some traits in common.
As with most big dogs it will be imperative to teach good manners. Any dog that size can simply drag you wherever he wants to go and it won’t even slow him down. Add to this the fact that this breed tends to be dominant and you will find that training and socialization is imperative. You don’t want him to eat the neighbor’s small yappy dog or the plumber either, and you don’t want his really loud, deep bark to make the neighboirs want to sue you. Starting out with a puppy training class is a good idea because it will help with all of these things.
Also, as asmonet said, they will migrate to cold floors wherever they can find them. One friend has a tiled front hall and everyone has to use the side door instead of the front door because the hall is always completely filled with dog.
Exercise is important to all dogs but especially to big ones, energetic ones and young ones. You and the dog will be much happier for two good walks a day. However, depending on where you live you will need to time them to avoid heat and high humidity. Also, big dogs tend to have more skeletal and joint problmes so you will need to keep an eye on him as he exercises. Our bulldog injured her ACL when she was a puppy and her owner at the time did nothing about it. As a result, when we got her we spent $2500 repairing her joint. Unfortunately, the injury happened when she was still growing so the bones are deformed, but the leg is usable.
Also, you will learn never to leave things you care about or that your dog will like on counters or tables. Hide the bread in an upper cabinet and never, ever leave anything out to thaw. It will not be safe.
Depending on the dog, a bunji cord on the fridge could be an excellent idea.
And get a really good vacuum for fur, and learn to either love vacuuming or love fur-covered furniture and floors. Many folks like the Dyson DC-14 Animal for that.
Finally, this breed loves their people and wants and needs to be with them all the time, so they are NOT a good “yard dog.” They are working dogs, bred to herd cattle and pull carts, and will be bored if left with nothing to do, so be sure to figure out ways to keep that smart brain busy.
Hope this helps!