More or less the happy sense of being proved right. Since the Higgs is well-modeled and well-understood in theory, other than the value of its mass, we already have a rudimentary scientific understanding of what it does and how it works. But it's critically important that these theories, like the Standard Model that predicts the Higgs, be experimentally confirmed--though you are right that it would be far more earthshaking if it didn't appear.