Having had a day to think about it, I'm still not sure I'm sold on the idea of Paul Ryan as the ideal running mate for Mitt Romney. I think Ryan is great, but I suspect having him in the VP slot will be more beneficial for campaigning than it would be for actual governance, should Romney win the election.
Ryan is very well situated in his position as chairman of the House Budget Committee. He's really set the policy and intellectual tone for the Republican Party for the last three years. If Ryan goes to live in the Naval Observatory, the new chairman of the House Budget Committee would likely be Scott Garrett, a congressman from New Jersey. Garrett is about as reliable a conservative as a New Jersey congressman could be, but he's not exactly a high-profile fellow. I think Ryan's leadership would be missed.
Every president swears that they will find a substantive role for their vice president, but veeps usually end up getting sidelined. Dick Cheney was an éminence grise for George W. Bush, but Joe Biden has been more typical -- a guy who goes to funerals and serves as a punchline for Jay Leno jokes. In this model, the buffoonish Joe Biden is perfect -- Biden has been a combination of Spiro Agnew and Shecky Greene. It would be a shame if Ryan found himself in that position. It will be important to pin down specifically how Romney would deploy Ryan.