On freebsd you can run a very reliable console server using :
conserver-com-8.1.16|/usr/ports/comms/conserver-com|/usr/local|Application that allows multiple users to watch serial consoles|/usr/ports/comms/conserver-com/pkg-descr|kuriyama@FreeBSD.org|comms|||
http://www.conserver.com/|||
(ports INDEX line)
I ran two 8 port pci cards on one machine that were supported under the puc driver. In many ways it was way better than some of the commercial solutions.