it depends on how susceptible a particular breed is to specific genetic diseases. the more issues a breed has, the more important it would be to me when considering buying a dog or puppy.
generally speaking this kind of certification is an excellent thing and shows that a breeder truly cares about improving his or her breed of choice and doesn't just breed for profit.
sadly most people still buy puppies from pet stores and irresponsible breeders, neither of whom will "waste" money on certification. in addition to that, dogs have to be of a certain agre for certification and irresponsible breeders tend to breed even before they reach that age.
more info:
http://www.offa.org
http://www.vmdb.org/cerf.html