How accurate is Jim Cramer?

I've watched his TV show periodically. And I can tell you that I come away with the idea that Jim Cramer is load and very over-opinionated. All that aside, I've never been able to determine how accurate his "analysis" actually are. Is he able to sway the market with his comments and suggestions? I'd be curious to know. Because if I became an avid viewer of his show or a purchaser of his book, what would I actually learn?