If you want to route things at speed why use something based on an anemic ARM chip running a few hundred megahertz when you have a multi gigahertz cpu at your disposal? I just dual-port my main computer and have it route and nat things. Routing works at least to 700 Mbits/sec. If I ever move to a country where gigabit ethernet to the home is available at a reasonable price (like in Japan where it is ~$100), then I'll have to revisit the routing situation.
(My setup is an athlon64 at 2Ghz, two linksys pci gigabit ethernet cards, fedora and iptables doing the NAT-ing. The computer is on 24/7 anyway because it serves web pages and accepts my email, so having it do the routing doesn't really increase my power bill. If power ever becomes an issue, I'll just move the server to an old laptop which will cut my power from 80watts to 20watts. That admittedly still isn't as low as an ARM chip, but you do get quite a bit more performance for your money.)