Speed also. Your hub client is way faster now that you moved from Ruby to Go. Doesn't mean Ruby was a bad choice, IMHO it helped you iterate faster on the initial product/prototype. I think both compiled and scripted solutions have their place in software development. What editor do you use at Github to write Go code?
I feel like there have been a lot of blog posts and HN discussions about the merits and downsides to Go, and I don't really have anything new to add to that.