I don't think that Ryan is boring at all. He speaks well and has excellent command of the issues. The most "exciting" thing about a politician is the enthusiasm he can bring out in others. If the pick is Ryan, he will bring out many conservatives who are holding their noses and voting for Romney. Ryan is also a Catholic and that group feels under siege right now with Obama's HHS rulings, and I bet many moderate and even Dem Catholics will be tempted to vote for Ryan.
I agree that McDonnell has a better resume (successful governor, Lt. Col in USA/USAR, etc.), but Romney and McDonnell together is a bit too similar appearance-wise (Romney is 65 and McDonnell is 58). Ryan adds some youth to the ticket, and I believe that he and Scott Walker can deliver Wisconsin for the Rs.
Paul Ryan has always amazed me with his knowledge. He has a way of making boring subjects such as budgets and finances not only understandable but interesting as well.
I never found him to be boring.