I found this, oddly enough, linked from a conservative blog. It talks about Biden's immense success as a law professor and the amount of respect his students have for him.

Robert Hayman, a professor at Widener who has taught alongside Biden since 2003, agreed with the students that whatever his gifts as a legislator or politician are, he has made a reputation as a "terrific teacher."

"He obviously knows the subject matter very well, and he's a gifted speaker," Hayman said Friday. "He has a real passion for the subject. He's a real student of the Constitution."