Jamelle Bouie has good reasons to think Democrats couldn't have passed Don't Ask, Don't Tell repeal by introducing it during the relatively brief period when they had 60 votes. (Kevin Drum adds that the 60 vote majority was only functioning for 14 weeks of Senate time total.)
Like Mad Men, the DADT repeal campaign is a window to how things were in less enlightened times. Back in the 1950s, the filibuster was being used to block progress on another civil rights issue -- equal rights for black people. Even if the country had moved far enough that a majority of Senators supported progress, a committed minority could still block the legislation with 60 votes. This week's action shows why the filibuster is an especially big problem for progressives, just as it was back then.
We're trying to change laws that are based on prejudices that most Americans may have moved beyond, but which people wrote into the laws a long time ago. Conservatives, on the other hand, are trying to keep those prejudices in the laws. Things that keep people from changing the laws are bad for us.
I've seen a lot of frustration directed at Democrats after the failure of DADT repeal. Really, Republicans should be the target of the frustration here -- no Republican voted to end cloture, and the only Democrats who did were from Arkansas. But if you're looking for villains beyond Arkansas on the Democratic side, you can also point at people like Chris Dodd who support the filibuster and try to keep their colleagues from getting rid of it.