That should make the race a little more interesting than if Romney had gone with Portman or Pawlenty. I like Ryan's tone and demeanor. This is more-or-less the pick many people expected given Romney's position: slightly down in the polls but not desperate. Ryan's a bit of a risk, but not a huge one.
I'm not so sure he'll crush Biden in the VP debate though. He looks young and he sometimes talks like an economics professor. Biden looks old and has a down-home, folksy dialect. When it comes to changing medicare, I expect that seniors will identify much more closely with Biden than with Ryan. That could hurt, potentially.