I think it's massively less ambitious, which is a good point in its favour.
Which raises an interesting point: what to people on the outside looks like a paradoxical combination of insane hubris and deep technical conservatism is probably simply what to Google's eyes looks like steady-state, responsible technical problem-solving -- c.f., hhvm and Facebook for a similar approach.
And Kotlin's is "compile faster than Scala"!
For those that don't know this feature is called structural typing: http://en.wikipedia.org/wiki/Structural_type_system
Also, OCaml uses structural typing too.
The fact that mainstream developers don't know it, does not make it something that Go designers invented.