Bernard studied hard. He was ridiculed as a high school boy because of his "nerdy" behavior. However, he became a successful lawyer. He is happy with his life, and financially secure. This is ironic because of two things:
1) he became successful without the popularity and good looks that Willy thinks so important to achieving the American dream. Willy still ridicules him, but out of envy now, not a sense of superiority.
2) Willy's own sons are unfilled and unsuccessful, particulary Biff, who possessed all those qualities that epitomize an American "winner".
Miller uses Charley and Bernard as foils to Willy and Biff, letting readers see the fallacy in the American Dream and the potential of hard-working and studious Americans to acheive success.