I think it's interesting that a number of people felt that two advantages with puppies are bonding and molding the dog from day 1, and one disadvantage of adults is that there could be 'issues.' I've never had a puppy, so I'm not really qualified to judge, I suppose, but I find that the younger the dog I've adopted, the longer it takes to bond. My oldest adoptee stepped out of the shelter and decided I was her puppy - I don't believe they make bonds stronger than that. My youngest adoptee believe she is my puppy, and
it took us about 5 years to really bond. I've never been a big fan of the whole idea of molding anyone, from dogs to kids. To me, the inevitable foe of molding is summed up in "Man plans, God laughs." As to issues - well, it's not all nurture. A good, responsible source is a good, responsible source, whether it supplies mostly puppies (breeder) or adults (shelter). A dog from a good shelter doesn't neccessarily have more issues than a puppy from a good breeder. You get a big bonus in an adult dog because you can see what they are, and don't get blinded by puppy cuteness and puppy formlessness.