Smoothwall is a good idea, I use Clear OS formerly known as Clark Connect. Both offer way more then any home router. I do have a home router but it just an AP now because it is cheaper then an AP. I do like the Linux solution as I can have a proxy, antivirus, intrusion detection, PPTP or SSL VPN endpoint, web server, NAS, DLNA server, and even more rolled into one. Then VPN has been great for road warrior access to files and remote desktops that I would never trust a simple router or hosting site to perform.
A lot of people I know have these routers I recommend having one over directly hooking a PC to any broadband connection, even if you aren't sharing the connection. I will have to check my friends and family to make sure they have changed their passwords.