Just because you're below the Legal Limit. It doesn't mean that you're safe driving. Even a small amount of alcohol slows your reactions, no matter how well you can hold your drink. We're only talking fractions of a second here. But it can be enough to cause an accident, particularly if you're on a fast road.
And I wouldn't take that 2 Pint Limit, too seriously either. A friend of mine, lost his license after drinking only 1 Pint, before driving. It all depends on your size, and Metabolic Rate. It just isn't worth it!