I used Smoothwall a couple years ago and it was great. I switched to Astaro because it has caching. (DNS and HTTP) Astaro also has a VPN server and can be setup as an endpoint.
Astaro free for home use is restricted to 10 hosts though. The pay version brings web and mail virus filtering.
Astaro has steeper sys req than Smoothwall but I'v been using it on an old dual proc P3 Dell workstation for some time and its rock solid.
This IPcop looks pretty good. I can't find a list on their site of what services it uses. It appears to do webcaching with SQUID but what about a DNS cache? Anything else?
Traffic shaping looks cool.
**mOnOwall looks way more impressive than it used to, also. I may have to switch over to it.