Grubbylabs is correct regarding pedigree.
When I'm looking for a puppy to purchase I ask a lot of questions regarding pedigree and health clearances. I also expect that I'll be furnished with these answers in writing - proof basically that what I was told is correct. If these prove to be false later on I have something I can fall back on to correct the issue.
The problem with AKC and other kennel club certs is that for the most part dogs were never really bred to very strict standards. Basically if your dog LOOKS like the breed you claim it to be a you can have "experts" claim your dog is that breed you can get at least a provisional registration for the dog as being purebred. A couple generations later you can start breeding the progeny of that dog so long as you'd bred it with other purebreds of that breed... there is no scrutiny regarding genetic defects, diseases etc. I know that each club has standards that one must adhere to if one is to compete with the dog but there is nothing within those rules and standards regarding the breeding of dogs that are genetically defective. The other thing is that those standards regarding the breeds tend to be nothing more than cosmetic and does not truly address the issue of genetic problems.
That being said I won't purchase a puppy UNLESS its AKC registered or registerable. At least then there's one more layer of assurance that at least the dog is considered a purebred.
As grubbylabs said if you're getting a high end hunting dog there are a whole host of issues you as an average dog owner may not be able to handle. High energy levels is one of them. There's also the very high prey drive. Add a high level of intelligence to the mix and well that's a good recipe for trouble. Be aware of that and know the fact that you will be getting that - and if there are any genetic problems or diseases with your puppy then you can add that to the mix too.
This is who we are, what we do.