I'm not sure I can agree about generics. In many cases Go code is already fast enough, so other things come to play, especially type safety. Prior to generics I often had to write some quite complicated (and buggy) reflection code to do something I wanted (e.g. allow to pass functions that take a struct and return a struct+err to the web URL handlers, which would then get auto-JSONed). Generics allow to write similar code much easier and safer.
Generics also allow to write some data structures that would be useful e.g. to speed up AST parsing: writing a custom allocator that would allocate a large chunk of structs of a certain type previously required to copy this code for each type of AST node, which is a nightmare.
