"The Big Bang" does not side-step the infinite regress in the same way as the uncaused God of the Christian philosophers did. Christian philosophy asserts that all things have a cause, but God is perfect and so is able to be a cause in and of himself. The assertion is that anything that is perfect can be externally uncaused and still not violate the laws of causation. The modern version of the "Bing Bang" however is founded on quantum mechanics, which holds that there are circumstances where causality does not apply.
The infinite regress is crucial to all areas of philosophy, including epistemology, ethics, and aesthetics. I will use ethics as my example. A moral philosophy can tell you whether something is good or bad. But what if you want to know if a particular moral philosophy--say, that of Nietzsche--is moral? You then need to make a meta-ethical judgement. But what is the moral value of the system used to discern the moral value of Nietzsche's philosophy?