Undeadly.org mentioned the following highlights:

"Selected highlights include:

* Support has been added for qcow2 images and external snapshots in vmm(4)/vmd(8).

* "join" has been added for Wi-Fi networks.

* Security enhancements include unveil(2), MAP_STACK, and RETGUARD. Meltdown/Spectre mitigations have been extended further, and SMT is disabled by default.

* rad(8) has replaced rtadvd(8).

* bgpd(8) has undergone numerous improvements, including the addition of support for BGP Origin Validation (RFC 6811). smtpd.conf(5) uses a new, more flexible grammar.

* For the first time, there are more than 10,000 (binary) packages (for amd64 and i386)." [1]

[1] https://www.undeadly.org/cgi?action=article;sid=201810181400...