Looking for an alternative, I came across this: Leopard contains a second firewall called IPFW. It is an open source program frequently found in the Unix world. There is a graphical frontend for it called WaterRoof (not „waterproof“!).
WaterRoof is an IPFW firewall frontend for Mac OS X with a easy interface and many options. Features include dynamic rules, bandwidth management, NAT configuration and port redirection, pre-defined rule sets and a wizard for easy configuration.
Nice little thing – makes IPFW administration quite simple.
Apple, could you please throw away your current firewall UI and replace it by something for adult IT people? Thanks!