Last year - new stuff in 4.0 and 4.1

pf(4) supports Unicast Reverse Path Forwarding (uRPF) checks

multipath routing
use more than one path to a destination
link aggregation on layer 3
works even with distant networks

carp demotion counter
Demotion of a carp interface from userland.
The counter can be increased in case an important part of the system fails (partial failure)
a less degraded system becomes master
independent of advskew