I went and looked at a flock once with my DH as we were seriously considering getting them.
The man who owned them said that he was surprised I wanted to use the cow for a milk cow. Apparently they are considered a meat breed. He showed us his bulls and cows.
Standing next to the animals, I was amazed at how HUGE they are and how intimidating their long horns are. I recommend you stand near one before finalizing your decision. We decided against it because of the horns.
They are definitely gorgeous animals, though.
All the rest of my knowledge of them was just from the internet and I have forgotten it....
(Oh- except for the fact that they are supposed to be really good foragers and can survive on pasture/weeds that would starve a regular cow to death).