Almost all pet stores buy from puppy mills, even if they say they don't. Just ask to meet the breeder and see their reaction. Too many pros to mention ... they just love you and you love them back. Cons: People should consider an adult dog more often. My last terrier-cross was adopted at 4 years old and lived to be 17 years! I now have two from the Humane Society, they make life more hilarious.
My spoodle and little terrier are rescued dogs, and worth their weight in gold! Why would you pay out for a designer dog when you can get one who really needs a home for so much less? Cons: Any good shelter will allow you a trial period to assess whether this dog is the right match for you and alleviate potential problems. You cannot loose this way!