IMHO: HHVM/Hacklang are cool and i appreciate Facebooks contributions to building a better PHP enviroment... but at the end of the day, it feels like someone trying to put a V12 engine in a golf cart. It's cool if you are already driving a golf cart, otherwise it's weird.

So if you have the chance to start fresh: choose Java or Go. Or anything else... (define "performance"?)