It works in the MS compilers. It's also perfectly stable, it's what COM is based on, and it's used in very substantial and complex applications.

"Runtime binding"? I think you mean deciding what method to call, based on the type, at runtime? Aka polymorphism. You'll still get the inherited functionality just using standard inheritance, yes, but thats not the point.

The interface functions do not have two different calling conventions at all. They both use the standard C calling convention. The body of the function is totally irrelevant.