I've finally installed OpenWRT. And I'm very happy with it. I've just been struggling quite hard with the nas binary (Nas is the closed source tool from linksys that sets up WPA)
I've added my 2cents in the OpenWrtFaq :
Don't use -l switch if you are not using the bridged mode of the router. Indeed, In this case nas silently fails as far as I can tell. '-l eth1' wont work