I'm confident that Jim DeMint's resignation matters, although to be honest I'm not exactly sure how. At the very least: as I always say, ever Senator counts. DeMint's replacement will vote about how he votes, but there's more to being a Senator than floor voting -- as DeMint's career demonstrates.
Something that doesn't matter? Well, I already talked about the super-early 2016 polling, but I'll stick with that.