Has anyone had any luck setting up ppp with NAT or with dualethernet cards?

It is very easy to do on OpenBSD (v.good how to's) but I don't find FreeBSD that helpful.

The man says to enable pppd with -nat, which is fine but I'm not familar with the syntax of the rules or where they should reside, or even how to start pppd with nat (apple does it).

OpenBSD has a rules file in /etc. You basically add:
192.168.0.0/24 -> interface

[fitter]

Go here:

http://forums.macnn.com/cgi-bin/Foru...ML/000133.html

It should have all the information you need.

Yep that does the trick. Quite easy. However I was unable to start natd before ppp0 was enabled through the ppp connect. Perhaps another line has to be added, something like:
ipconfig ppp0 up?

OpenBSD allows you to set up a range of ports for natd instead of just one... how is that done?

In OpenBSD you do (in /etc/ipnat.rules) eg
map ppp0 10.0.0.0/8 -> ppp0/32 portmap tcp/udp 10000:20000

OpenBSD is a lot better than FreeBSD in ease of use, security, and installation, surprised Apple would not have used that as its base.