Randolph Update 2018/10/10: I now use IPFire for all the same reasons I used SmoothWall in the past.
What an obliviot I am! I upgraded the firewall from SmoothWall Express 1.0 to 2.0 at the end of last year, and to test out some of the new functionality, I noticed a certain IP address was seemingly attacking my network, so I blocked it.
Today, about a month later, I discovered that the address was that of SmoothWall’s own website. I couldn’t visit the URL, I couldn’t download updates, nada. So now I feel silly. But I also realise that even SmoothWall’s website being blocked proves how reliable the product is. Download it for your network. I endorse it.