And I don't make any real defense of some of the darker corners of XML. In particular, I already criticized entities being a bit too much. Namespaces are also something that, while I can see the desire, the implementation is way too much for most of us.
JSON schema is going to be cursed for a long time. Just the odd treatment of it will be a problem. (In particular, that it is a subset of the numbers that javascript itself supports is... awkward.)
I also confess, though; that I'm not clear why I would want a null in the middle of a string? That feels like a gun loaded and aimed squarely at a foot.