OpenBSD 5.6 is the first version with LibreSSL (OpenBSD's cleaned-up fork of OpenSSL). Only user-visible change: openssl(1) moved to /usr/bin.
And of course, under the hood, a lot of epic cleanup. Cue Bob Beck's BSDCan talk
Also see Bob Beck's LibreSSL first 30 days (on YouTube thanks to Jason Tubnor) and stay tuned for presentations during the conference.
But https://twitter.com/yinettesys/status/514322389060943873