I 'love' my net4801, so these would be my answers. Apologies if they weren't questions
Installing:
I do it the easy way, which is to plug a Compact Flash card into an CF - IDE adaptor on a larger faster computer, and proceed the usual way. It isn't much harder to do it the tftp way of course:
http://www.xinu.nl/unix/soekris/net4801/
It refers to FreeBSD-4.8 but I'm sure the information would apply to more recent releases. I'm running 6.3 currently:
> uname -a
FreeBSD soekris.*****.co.uk 6.3-RELEASE FreeBSD 6.3-RELEASE #1: Tue Feb 10 20:32:25 GMT 2009
john@soekris.*****.co.uk:/usr/src/sys/i386/compile/SOEKRIS-BRIDGE i386
Maintenance:
Easy enough as soon as sshd is up and running. I managed to break it once by trying to source upgrade from 4.n to 6.n. Completely forgetting that half of the file system (/var, /tmp, /usr etc.) was on an external USB drive!
There are a few adjustments necessary to make the entire POST and booting process visible on a serial terminal, which I'll dig out of my notes if anyone needs it.
Applications:
Mine served as firewall (pf) and mail server (sendmail) for about 4 years non stop, but these days I use it for simulating bad network links with a dummynet bridge. It's ideal for that, as sis0 is on the LAN and sis1 and sis2 form the bridge.