At the moment, most of the things that are spec'ed in the box are the gnarly macro "languages" like destructuring, defn, ns, etc. These spec'ed macros do catch a far more complete set of error messages than the macro did with custom error handling. However, those error messages are in many case more challenging to read than before. This is an area of ongoing research - the reasons for the complexity are varied. In general, specs for core functions are much simpler and provide much better errors, but we have not focused on adding those yet. This is why some of this stuff is still alpha!