And it's been used by many commercial networking and storage appliances too. Juniper using various devices (routers, firewalls, switches, etc), Citrix Netscreen load balancers, Dell storage Isilon just to name few. Knowing FreeBSD pays dividends if you work enterprise gear. Makes your life so much easier even there is vendor specific UI's and shell, but you know your way around so much better when you encounter any issues which requires using shell and it helps you debugging things you would otherwise not being able to accomplish.

Knowing you way around *BSD how check things, mount a USD drive, collect data & or evidence when need arises is well worth having beyond just surviving bare Linux skills. BSD's are alive and kicking on commercial appliances and devices.