after the initial batch all manufacturing resource was supposedly moved to the pi 3 so they're still tricky to come by. I'm sure they'll be back though. There's an interview in https://www.raspberrypi.org/magpi/issues/43/ that explains this I think. I have one pi zero and (like 99% of raspberry pis - or is it raspberries pi? - in the wild) I have not done anything useful with it yet.