As far as economic issues go, he's quite far to the left. The only thing I can think of that is odd is how he went after ACORN with a provision in a Student Aid Act in 2009 that would prohibit funding. Especially given how those videos doctored to attack ACORN were nothing but lies. That's the only really damning thing in his whole record that I'm aware of. On social and healthcare fronts the guy is definitely to the left having always supported choice, lgbt rights, legislation on wage discrimination, expanding the strength of hate crime laws, etc. is anti-war and wasteful military spending, believes in renewal energy etc. etc.
He's a generally good dude when it comes to the issues.