"Any sufficiently complicated concurrent program in another language contains an ad hoc informally-specified bug-ridden slow implementation of half of Erlang."
Edit: I'll add, though, that the Go people are pretty smart and seem like they're doing good things, so I wouldn't be too complacent in thinking Erlang is the only game in town. It still does get some things right that are hard to replicate in Go, though.
The flip side of that coin is you're liable to get someone reinventing the wheel - poorly - in whatever language doesn't have all those goodies.