Barack Obama and Dmitry Medvedev have signed a nuclear disarmament pact that reduces American and Russian nuclear arsenals by 30%. This is very good news in the short term, as moves toward disarmament make our nonproliferation efforts more credible with other countries and show emerging powers that international prestige isn't about having the biggest nuclear stockpile. And it's very good news in the long term, as progress on this front makes the human race less likely to totally annihilate itself.
I'm optimistic about the future of humanity. For those of us in the developed world, living standards are way better than they were centuries ago. Over the course of the 21st century, I think we'll see people of many other regions come to enjoy the progress that Westerners have made in the 20th. The rate of technological progress is accelerating. This progress will continue until humans in the millennia to come (and possibly all sentient beings, since with our future technology we'll have the resources to undertake some really ambitious world-improving challenges) will be living lives of truly freakish awesomeness.
That is, unless humans go extinct before then. As I write this, it strikes me that there's a pretty good utilitarian case for being a single-issue nuclear disarmament voter. Millions of years of utopia are worth a lot in the calculus, and the best thing we can do to make sure we get there is to not destroy ourselves first.