Basically, I don't know how anyone can justify spending $1000+ on a genetic mixed-bag that may or may not be "the perfect family pet." The premise behind a designer dog is to take two breeds that have desirable traits (say, the intelligence and hypoallergenic coat of a poodle and the loyalty and work ethic of a Golden retriever), breed them, and out come puppies that are better than either parent. The truth is, genetics just doesn't work like that. You can't pick and choose which traits the pups will take from either parent- you could get a hypoallergenic goldendoodle, or you could get a perfectly allergenic one, depending on which coat type the pups end up with. More than likely you'll end up with something in the middle, although good luck marketing your "partially-allergenic" pet doodles.
The doodles I've met at daycare are uniformly unique, each one different in coat type, behavior, and personality. Although they're only supposed to get the good characteristics, they also often pick up bad traits of both their parents' breeds- in particular, the labradoodles all seem to take the barkiness and mouthiness of a poodle and combine it with the hyperactive, bull-headed nature of a lab, leading to a bitey, uncontrollable big dog that barks incessantly.
My favorite point of the above-linked article is that, while "designer dog" breeders like to say that their pups will be less prone to genetic diseases due to hybrid vigor, the opposite is more likely. Think about it- if your mom's family has a history of skin cancer and your dad's family has a history of heart disease, do you consider yourself more healthy than either one because you'll get your mom's good heart genes and your dad's good skin genes? No, you consider yourself predisposed to both diseases, because you'll get a mix of genes from your parents. The same goes for designer dogs.
If you want predictability in appearance, behavior, and predisposition to particular diseases, choose a purebred from a reputable breeder. If you want a dog that is least likely to develop genetic diseases, and has a unique appearance and personality choose a nice Heinz 57 (and give a shelter dog a forever home!). If you want to spend a lot of money for an unpredictable pup with just as great (if not greater) a predisposition to genetic diseases as a purebred, get a designer dog.
Not to say that the doodles and dachsi-poos and shi-chis and all the others are worth any less as pets and family members... But when mixed-breed dogs are dying in shelters, how can any responsible breeder bring mixed-breeds into the world just to tap into the "designer dog" trend?