Vilsack was a substandard governor that mostly got by due to Brandstad fatigue. In practice his priorities were skewed towards pet projects and lacked perspective on the grand scale. He brings nothing of much use to the ticket and I suspect that the more folks like me (heavily left leaning types) learn about him the less enthusiastic they'll be about him. I'd rather have Al Gore be Clinton's VP pick.
They say the first rule of picking a VP is to do no harm. A pick of Vilsack will do harm with me. If Clinton wasn't going up against a fascist wanna be (which admittedly is most potential Republican presidents in my view) and she picked Vilsack, I'd laugh for a while then vote green because it will be clear Clinton doesn't know what the heck she's doing picking him. Vilsack should not be any where near the presidency. I was rather happy Obama put him in the cabinet because at least there he couldn't screw over Iowa politics further.
Yes, there's worse picks out there. But it seems most of them have already been taken off the table.
Hillary's VP (if she is elected) will be mega-overshadowed. Hillary will trust only her inner circle of Hillbots. In that case, having an anonymous figure like Vilsack as VP is not a bad idea.