I grew up with these dogs. Can't say enough good things about them - best dogs we ever had. And SMART, so smart.
We had one, Magnum, he killed a porcupine that wandered onto our property one day. Killed it. Had quills all the way down his throat, that was like a $1500 vet bill.
Magnum again - we were having trouble with the phone connection so my Mom called to have them come out but said do not come unless it's between these hours, we have to be home. Well, we get home the next day and there is this sign on our mailbox from quest and it says "attacked by large dog, will not return until dog has been confined"... so we figure ok, he drove up saw the dogs and turned around. So my mom is out in the yard later, and finds a qwest helmet. Freaks out - calls qwest. Turned out Magnum had been down at the barn, and the guy got out of his truck and made it to the electric box. Magnum came tearing out of the bushes, knocked him down and grabbed onto him, tore up his clothes - but never bit him. Not once. Magnum made the guy crawl back to his truck (wouldn't let him stand up) - and the guy got back in his truck and left.
One more Magnum - my uncle just bought a Suburban and drove up to get me one day - Magnum bit his tries and put teeth marks in them, while the car was driving away. Grabbed onto the tires, head spinning with the wheel and put teeth marks in them. I thought it was hilarious, my uncle wasn't so amused.
Yea - awesome dogs, for sure. Expensive but worth every penny.
Edit: Curious though, usually their ears are cropped and I noticed that yours aren't? Was that a preference or did the breeder not offer it? It's not for anything aesthetic, these dogs are known for fighting off large predators (bears, Mt. Lions, etc.) and those animals go for the ears which is extremely painful for the dogs, so they crop them.