Like pretty much every other programmer with a Mac, I'm currently looking at Swift. Will I write anything but toy programs in it? I don't know yet - I don't really write any Mac-ish software on my Mac, just unix-ish programs. If Swift doesn't escape the OS X and iOS ecosystems it'll be a nice exercise in a neat language that's not really that relevant to the world at large, or at least to my part of the world at large. Not that this sort of vendor lock-in can't work well - Visual Basic 6, anybody?
I hope Apple will open the language to be used outside its software ecosystem but from what I have read so far, it's tightly integrated into the iOS and Mac OS X runtimes so I'm not sure how feasible that even would be. Still, I'm pretty sure it'll remain on my list of languages to play with.