Yes indeed I have, and I have several problems with it, one of which is "Expires: August 3, 2013" with no new version in sight. My other major problem is that AFAICT it doesn't support one of my pet favorite features namely "Algebraic Data Types"[0, 1]. If you extend json-schema like Swagger has done it might support ADTs properly AFAICT, but I don't have any actual practical experience with Swagger.

[0] https://en.wikipedia.org/wiki/Algebraic_data_type [1] I should note that support for ADTs in XSD is sometimes sketchy in the various code generators, but at least the XSD specification supports it. (It could also be argued that XSD supports something even more general... which it probably shouldn't since ADTs basically cover the whole data structure space unless you go to higher kinds, inheritance and such.)