While I'm not offering my full throated endorsement yet, I do concur wholeheartedly with the sentiments of E.J. Dionne, and Ezra Klein on the positive attributes U.S. Senator Joe Biden (D-DE) would bring to the position.
Unlike some people, Biden doesn't just say he's a fighter, he's actually been one. And unlike some people, he's actually been a fighter against the other party. He can be, as Ezra notes, an obnoxious ass. But among other things, that is something this campaign will desperately need, since its leader can't afford to be one. Along with his pugnaciousness comes a willingness to say what he believes, come gaffe what may, lending an all-important "authenticity" quotient to the ticket. And the truth is he is about as knowledgeable a spokesperson on matters of law and justice, as well as foreign policy, as the party has.
If Biden can seem a bit unsufferable for all his media appearances, I think it's worthwhile to point out that U.S. Senators are not just voting automatons--they're also elected to inform, and hopefully lead, public opinion, not only in their state, but around the country. Or at least the best of them over the years have recognized the virtue in their playing that role. For this reason, you won't hear me gripe about all the times McCain shows up on Sunday talk shows and the like.
On the downside, Biden isn't exactly what could be called a fresh voice in the public debate. And to the extent that for Obama the promise of bringing in the new is a legitimately real aspiration--and I think it is, as it is for many of his voters and donors--then Biden as VP would not just be a potential mocking point for Republicans and late night TV hosts, but could actually represent a real digression from the campaign's goals.
So, although I have him in my top three or so, I'm not quite ready to annoint Biden. While the Party needs a tough and knowledgeable voice, it also needs a new voice, one that challenges the conventional wisdom on important issues.