I just read what will probably be the most comprehensive analysis of the Ryan for VP pick I'll see. Written by Sean Trende (great name) for RealClearPolitics, it gives a list of positives and another of negatives.
I won't try to summarize it, there's too much. If you're scratching your head wondering what the Ryan pick is all about, why he was chosen, here is the best set of answers you're likely to see.