What will impress me is if they say they won't obey it, PERIOD.
The problem with Republican governors saying they will ignore the law is that they will not be the governors forever. Some states will probably have a Republican governor for a good while, maybe like Texas. But if a Democrat replaces the current Republican governor, the law will just go back into place.
Same thing with defunding or Romney saying he would issue an executive order to nullify the law. These remedies are only temporary until another Congress or President is seated.