Yglesias weighs in on the new Senate balance:

In many respects the main significance of Franken's victory isn't that it brings us to 60 senators, it's that it increases by one the number of serious progressives in the Senate. But Franken or no, the balance of power still rests with a large block of centrist Democrats and Susan Collins and Olympia Snowe on the other side. The situation by no means dooms Obama's agenda to defeat, but it does mean that legislative outcomes are overwhelmingly likely to be a fairly pale shadow of the agenda a majority of the public voted for last year.

There's two different issues. The first involves the centrist block - Senators are islands to themselves, and Dem leadership can't herd them easily. Obama's agenda will always face resistance - but I'd rather negotiate with Senators in my own party than with Republicans.

Yglesias also mentioned the second roadblock: until Senators Byrd and Kennedy return to full health, Democrats literally won't actually have 60 votes.