He's an interesting choice. The whole thing reminds me of Tony Blair's decision to appoint John Prescott as deputy Primeminister. The Times today described how Obama presented binden as "a scrappy “working-class kid” who is as at home in a bar as on Capitol Hill." Very similar to the way an image conscious Blair played up Prescot's earthiness and experience.
As it happened, despite his political experience, Prescott proved quite incapable of rising to challenge of the job. Grittiness and experience proving a poor indicator of sound judgement. I think Obama is playing a fairly risky game here, I only hope it works out for him. As a European aware of the global significance of this upcoming election, I don't like the idea of a McCain victory coming as the result of a tactical misjudgement by Obama.
Certainly he could do without a scandal like this during the run-up period:
http://www.youtube.com/watch?v=4yG8buxb0lg