I'd compare the pick to JFK and Lyndon Johnson. That has its own unfortunate parallels, but it also has plenty of inspiring ones. JFK also got a steady running mate because he was horrors a catholic. And well JFK is part of the change on those opinions of religion.
I also like that Biden would probably be too old to run in 2016. That makes things a more open field. Women in office right now can plan for 2016. I would have preferred Sebillius, but this allows a competition which can reveal a lot.
One thing is that Biden's centrism and the fact that he has been on television forever is that he is a familar face.
Biden's pick says "Yes I am change, but it is a change based upon the previous foundations that this country has laid."
The fact that the voted for the bankruptcy bill and the Iraq war and that now he is running with a presidential candidate who was against those things is a symbol of change. Not just a change of leadership, but a change of opinions among Obama's opponents who are coming to his side.
Biden allows obama to set himself up as representative of the entire democratic party rather than just the most liberal half. Which is more important for winning and getting things accomplished.
George Bush's massive incompetence has not changed peoples views on the issues too much I think and neither did clinton's well run government do much before that. It made people change their opinions on the relative competence of the two parties, but not the issues. What Obama is trying to do is change people's opinions on the issues.