Slower in the short term while the code remains transpiled from C. Will get faster as the team goes over it a couple times.

Yes, this is a good summary.

> Builds in Go 1.5 will be slower by a factor of about two.

https://golang.org/doc/go1.5#performance

The small increase in build times doesn't bother me at all when I'm generating a binary, but unfortunately it's very noticeable and irritating when using tools like vim-go or syntastic which type-check/lint/gofmt your code. Using these now causes vim to be unresponsive for up to a second every time I save, whereas the delay used to be insignificant.

> which type-check/lint/gofmt your code

Those tools do not use the Go compiler. They're using go/ast or go/types. So the translation of gc from C to Go can't have affected them.

They also build the source file, which is indeed much slower, to about 2x.

Perhaps things have improved since then, but this thread indicates build times will regress a little:

https://groups.google.com/forum/#!msg/golang-dev/6obxRcm-rqc...