Well, I completed the normal installation and it all looked fine (installed network and firewall modules), up until the moment I configured eth0 and eth1 to be bridged with br1 using dhcp. This reconfiguration caused an error in zentyal (firewall) that I couldn't save anywhere (no text editor installed). Since that moment, my network configuration hasn't worked. Zentyal reports the correct configuration, but zentyal has no IP configuration anymore and the webpage is inaccessible as a result. I tried running "dhclient br1" which used to help on zentyal-2.3, but in 3.0 it fails with iptables giving this error: option "--physdev-is-bridged" cannot be inverted.
So, now I have a 3.0 install with no network configuration and no network access and no obvious way to proceed (except for a total reinstall).
I'd like to call this a huge bug. :-/