Yesterday I gave a talk about HHVM and Hack at the monthly webtuesday here in Zurich. The slides can be found here
It was a great evening, thanks to Netcetera for hosting it, thanks to Joel and the webtuesday crew for organizing it and also thanks to Johannes for chiming in when we talked about PHP internals.
If you have any question abut HHVM or related things, just ask in the comments, contact me on twitter or meet me personally, if you're nearby (aka in Switzerland).