The Go compiler is so fast you can use it the way you would a scripting interpreter ("go run whatever.go"); it builds the whole standard library in seconds. Every program I've written in it (topping out at around 20kloc) compiles instantaneously --- I can't perceive the amount of time it takes to compile.

C compilers are fast, but they aren't that fast. Go compiles so fast that it changes the way you write and organize code; you would never consider compilation overhead in any decision you made in a Go source tree, where you might do that in a C codebase. For instance, Go programmers routinely compile code, run it, and throw away the compiled binary! You wouldn't think it would be possible for compiler speed to be so much better than C that it would make a difference, but Go's compiler manages it.