So why even bother with all this? Why not just go buy a hardware firewall from CompUSA and be done with it? It's all about control, flexibility, and expense. The first Linux firewall I built was to replace a $200 hardware firewall. I needed to expose a web server to the Internet, but the only way to do it with that hardware firewall was to have the web server be part of the local network and tell the firewall to forward all(!) outside requests to it. Not a good idea.
Most hardware firewall/routers, even the really expensive high end systems made by companies like Cisco, are limited in some way as to what you can do with them. With LBU, you are in complete control of everything, and limited only by your hardware and imagination. For instance, what if you'd like to add another network interface? With most hardware firewalls, that may be difficult or impossible. But with LBU, it's easy and cheap to add another network card, (assuming you've got an open card slot). Sure, it's more work setting up an LBU firewall, but it's well worth the effort if you demand the ultimate in control and flexibility, along with high performance and low cost.
In conclusion, LEAF-Bering uClibc is an Open Source and very powerful Linux based software tool that you can use to build a robust and feature-rich firewall system with standard computer hardware. The installation and configuration will require some effort on your part, but in the end you will have a system that should accommodate the needs of most any small to mid-sized network reliably and without breaking the bank.