I've never understood why low cost router and firewall software has tended to use Linux rather than OpenBSD or NetBSD, which has by and large pulled the security advantages from OpenBSD.
I tend to use it for basic services (firewall, dns, e-mail) that I want to start with a decently secured base. It is actually pretty quick to install a server if you keep decent track of the config files and keep the ports handy.
I've never understood why low cost router and firewall software has tended to use Linux rather than OpenBSD or NetBSD, which has by and large pulled the security advantages from OpenBSD.