I didn't really know much about Biden until today. At first glance he seems like a really boring fellow, but then a closer look and it seems he's done some agreeable things, specifically his work on the Judiciary Committee (RAVE act, VAWA act, Biden Crime Law, college aid & loans, etc). But then you take an even closer look, and you find the obvious imperialist, on the Foreign Relations committee (Afghanistan, Iraq).
So take your pick. All in all, he's probably the better choice, considering the options, but as we all know, he's like Obama, and McCain, and Clinton, and like any other Demoblican/Republicrat, some pros, some cons. Electorally, he'll most likely help in 1) the Debate, 2) the 'experience' charge, and 3) Appalachia.