I'm all about rescue/adopting. Of my four guys (well, one guy, three girls, lol), the older two are breeder pets. I'm not talking about good breed either, unfortunately. They came from backyard breeders, but I can honestly say that I knew no better back then, and I know better now. Jake (the dog) is 9 years old now and he was bred on a farm with two herders (Australian Shepherd, Border Collie). His wasn't the worst case of backyard breeding, but as they say, no reputable breeder breeds mixed breeds. The second breeder pet was Willow, my 6 year old kitty. We had recently lost a cat and Willow was our first girl (we'd previously only had males). We got her from a free kittens ad in the paper, and now that we look back on it, it probably wasn't a good idea. Willow is a dilute tortoiseshell, so some of her personality comes from Torti-Tude, but she does occationally make me suspect if she's inbred or something. She's just so SENILE sometimes, lol (okay, not senile, but skittish, overreactive, territorial, and when she spazzes out, she SPAZZES out!).
The other two, both girl cats, didn't come from a rescue or shelter, but are technically rescues regardless. Buffy was born on the streets to a stray (or lost?) momma, and when the litter was roughly 3-4 weeks old, they ended up at the vet hospital. They all died, except Buffy, and she came to our house the day after her family died. She was 4 weeks old at the time (that we know for sure, we don't know for sure exactly what her earlier life was). Our last furkid is Molly, who my sister found stuck in a tree as a 5 month old (she'd been in the tree for at least 5 hours). We intended to just keep her for a weekend, until her owner found her, but nobody ever called and we ended up keeping her.
What I've found, personally, is that rescues tend to have the most wonderful personalities. Obviously, all animals have great personalities, but I swear animals who come from sad situations know it, and when they go to a good home, they know it. Granted, I have only 2 "rescues," but they both have the most personality; Buffy's a humourous, intelligent little tomgirl, and Molly is completely devoted to me and is the most gentle little girl I've ever met. I also post at rescue-oriented forums (such as petfinder.com forums), and I come across so many stories of the behaviours of previously-abused/neglected animals. They KNOW they've been saved and they show an obvious display of adoration for their owners.