The type system issues can also be seen in:

* you get a note that a map must not be copied, but you won't actually be prevented from doing so?

* iteration can't use the native construct (no generic interface -> no generic iteration)

Another concern (big or little depending on your circumstances) many common things stored in maps, strings, primitives, incur an allocation on conversion to interface{}.

Coupled with a fairly inefficient GC it means I would need to think twice before using this.

Well, you might not want to put it in a public API anyway since it shouldn't be copied.

Better if you wrap it somehow. Then it's similar to an unsafe section; you need to be careful but it's self-contained.