I've heard it mentioned that their dogs are a bit unstable temperament wise.. and they do discuss this "rumor" on their website mentioning:
"We have occasionally produced a dog who is not friendly with strangers, and a dog like this requires a lot of socialization to fit into some environments. Occasionally a dog never accepts people other than its family, and such a dog may require the owner to take precautions when people are around."
Could be just rumor or people ill handling the "working dog drive" but either way, it's something I would be cautious of
Other than that, I don't really know. I personally went a more show breeder route, so I don't know what to look for working breeder website wise lol