>If we're charitable and say that HHVM has gradual typing, then really it's just slightly better gradual typing than what PHP already has.
Isn't a mix of dynamic typing and static typing, being optional which you use, the definition of gradual typing? Wiki also seems to agree with this.
I'd say HHVM greatly improves on PHPs type hinting, which is rather basic, unless you want to recreate every basic type as an object. Also, with PHP type hinting, you can't specify types of Object attributes/variables, which you can in Hack/HHVM.