For any non-Gophers reading this: I write Go as my primary language, and have for the past two and a half years. I just timed the respective compilation speeds on a handful of my larger projects using both gc and gccgo (and tested on a separate computer as well just for kicks).
gccgo was marginally slower, though not enough to be appreciable. In the case of two projects, gccgo was actually slightly faster. The Go compiler/linker/assembler/stdlib are probably larger and more complex than the most complex project on my local machine at the moment, but I think my projects are a reasonable barometer of what a typical Go programmer might expect to work with (as opposed to someone working on the Go language itself).
The more pressing issue as far as I'm concerned is that gccgo is on a different release schedule than gc (because it ships with the rest of the gcc collection). That's not to say it's not worth optimizing either compiler further when it comes to compilation speed, but it's important for people considering the two compilers to understand the sense of scale we're talking about - literally less than a second for most of my projects. Literally, the time it takes you to type 'go build' is probably more significant.
