As a follow up to asking people if they are using HTML5 or not, I asked the people who are:
What features of HTML5 have you used on production sites?
These are the levels of popularity, from almost 3,000 voters:
Not a big surprise that using the new semantic elements (like <nav>) is the most common use of production HTML5. It's easy, it's hip, it feels good.
Right behind that are the new form features. I'm happy to see that, as these things are also very easy to implement and usability tremendously, as well as replace clunky-ish JavaScript methods (I'm thinking of things like range inputs and the placeholder attribute).
Third place is the audio and video features. I'm sure iDevices helped push that along, as using HTML5 is really easy and works on those devices. Fallbacks are now also easy to implement.
The least popular feature is cross document messaging. Also not a huge surprise as it's not all that common of a thing to need. I do think this is super duper cool though, especially as I've been working on a thing that uses it.
"Other" came in ahead of a number of other features, so apparently I've missed a number of HTML5 features that people are actively using. Please share!