I think Caprivi has pretty near nailed it. If you have cattle for them to work they are great: they'll do it beautifully and go hard all day. As pets though they go nuts, and they'll engage in all sorts of destructive behaviour if they don't have work, and a lot of it. Ours on the farm would go out and work the stock by himself if he had nothing better to do, or herd the chooks.

They can make a reasonable pig dog, and ours liked catching and killing foxes. They tend to be a bit nippy too, but they are intelligent and can be trained. Definitely an outside dog though.