Not the only thing that mattered, but I'll go with the obvious one: the Senate going nuclear is a very big deal.
What didn't matter? I'll stick with filibusters, and agree with Adam Ramey that if the legislative filibuster goes, it's not going to matter much...as long as there's divided government. Although even then, "less than you think" could still be a big deal, so I suppose this isn't a very good "didn't matter." Sorry; I've been so focused on the nuclear business that I hardly know what else happened this week, and all the things I can think of actually did matter.
But maybe you have more. What do you think mattered this week?