Ask HN: Having Trouble with Google Public DNS?

There seems to be something intermittently wrong with this since approx 7pm GMT 7th April - maybe a bit longer. I'm not seeing any announcements, but several others having similar issues - https://twitter.com/search?f=realtime&q=google%20dns&src=typd . Doesn't seem to be geographically isolated; I'm in UK, seeing complaints about US ISPs as well. Anyone know what's going in?