Senator, erist, not governor, but that's correct -- he had a superb record in 2008. This is part of why I think one must pay attention to him.
Of course, that doesn't actually prove he's not biased, for two reasons. (a) He could always have changed due to bias, conscious or otherwise (he's tweaked very substantially with his model since '08); and (b) his model gives higher weight to things like the economy, past electoral patterns, etc. the farther out from the election we are, and converges, as we get close to the election, to looking mostly at the polls. So he could be completely wrong about how to factor in the economy, and then the numbers could all change in the last week or two based on that dropping out of his model, and if the model accounts for polls _correctly_, then he would get to say he had called everything right (yet his predictions this far out might be worthless).
I don't especially think that's the case though. But they're points to keep in mind when evaluating Silver's model. (It's to his credit that he's as transparent as he is about how it works, so that people like me can raise these points).