"checked" under Future Work has compelling use cases

[domenic]

In particular, making a custom element checkbox control.

[cookiecrook]

Yes, I agree. We should move this to 1.0.

[cookiecrook]

This was previously covered by value (usually 0/1, and occasionally 2 for "mixed"), but the editors discussion conceded the usefulness of keeping the more discoverable "checked" pattern. We'll look into how to describe that value is precluded by checked on checkbox and related elements. Edits should take care to ensure non-conflict with ARIA.

[minorninth]

I think I'd prefer "checked" to match ARIA

The fact that some platforms use "value" instead of "checked" is a platform-specific implementation detail. On the web, we have a checked attribute and the AOM should be no different.