The Pros and Cons of the Paul Ryan Pick

Pros:

1. He's a statesman - Paul Ryan is principled (whether you agree with those principles or not, he promotes the Ryan Plan regardless of his audience.) This is exactly what Romney lacks. (See #1 of the Cons below.) Ryan can help Romney rise above the fray of the immature and irrelevant campaigns both have become.
2. Tea Party candidates have been winning elections to both state and national offices around the country, and the 2010 Congressional elections indicated a strong repudiation of Obama policies during his first two years in office, as well as a repudiation of establishment Republican statist ideology. This implies that more and more voters are rejecting Obama's collectivism and big government ideas in favor of less government intrusion. Romney needs to drill this home. Yes, this election is about what kind of America we want in the future (though neither really does anything substantiative about spending): The Obama top-down collectivist policies where the federal government imposes more and more control over our economic lives, including borrowing more and more money from future generations to give to political allies, all the while exacerbating income inequality by enriching the political class and their cronies, or to begin devolving power from DC to the states and to the people. Romney needs to make a better case for his tenure at Bain Capital and how his experiences taught him how to find solutions and resolve problems, not avoid them.
3. Unlike Biden and Palin, Ryan is articulate and clear and comes across as intelligent, making digestible complex policy proposals and problems. If Obama is going to defeat any benefit Ryan brings to the Romney ticket, it must start by attacking the person, making him less credible so he doesn't have an opportunity to sway voters by making clear what a Romney/Ryan ticket offers as remedies for the fiscal problems we face. Obama obviously doesn't want to address them, so he must attack Ryan before the Ryan/Romney Romney/Ryan campaign can articulate the issues and their proposed remedies.
4. Ryan is disciplined and stays on track; it's about policy. Similar to #3 above, Ryan is not likely to avoid talking about the issues, hoping instead to beat irrelevant talking points into the ground. Instead, he'll remain focused on the issues, articulating well their ideas for possible solutions. This is what Obama cannot do given is record over the past four years.
5. He'll appeal to voters in some swing states in the midwest.

Cons:

1. Is Ryan a complement to Romney or will he simply upstage Romney and expose Romney's lack of principle (or allowing the Obama campaign to belabor this point)? Unlike Romney, Ryan has a principled vision. Will Romney endorse it, which exposes his lack of one, or will he back away from it, which then begs the question of why he picked Ryan to begin with. 
2. As I noted here after the mid-term elections in 2010, it's easy to talk about cutting government in the abstract, but when it comes to explaining specifics, voters turn on you. Ryan discusses specifics, which gives the Obama campaign a huge stick with which to beat up on a Romney/Ryan campaign. 
3. Some speculate that Ryan makes Romney less attractive to voters in states like Florida and Virginia, but I don't buy it. Marco Rubio has done very well in Florida and he's as economically and socially conservative as Paul Ryan. But Rubio doesn't have a record like Ryan has, nor has he laid out specifics of how to deal with the fiscal problems we face like Ryan has. This will be an interesting race.