Does the BGW320 still perform NAT with IP Passthrough?
Does the BGW320 support true bridged mode, or does AT&T offer any device that does?
IP Passthrough is not always the same thing. On the Arris routers AT&T also uses, this mode still involves NAT, which destroys packets and causes your service to be useless when hosting your own services (mail server, remote access server, etc.), or trying to setup a point to point VPN when using a third party firewall / router behind it.