You can use rPis for router duty; but they are kind of a tepid fit: the substantial RAM bump and option for actually-useful amounts of storage make them quite handy for situations where you are adding additional functions to the job description; but they rather poorly qualified for router stuff: NICs hang off the sole USB 2 port or i2c, and nothing integrated into the SoC, no PCIe options, GPU and video output that generally goes to waste in that application.
The AR9344 that I think these guys are using, by contrast, is a weedy little MIPS core at 530MHz; rarely featuring more than 128mb of RAM, and less flash; but it provides 2.4GHz wifi on-SoC, plus multiple 10/100 wired NICs; and PCIe host and peripheral support. Not a good choice if you need your node to cache or serve substantial amounts of stuff; but router SoCs are pretty good at what they do; and quite cheap; just generally hard to get with much RAM, graphical capabilities, or vendor-endorsed 3rd party firmware development.
