Trevor, the wrt54g is just doing DHCP to the FIOS router, no PPPoE etc. I don't recall futzing with the setting much, it just sits there are works, though apparently slower then it should.

I've slapped the current Tomato on to it, and will see if that makes a difference - must wait until SWMBO is finished watching TV before I swap routers.

edit: it is possible that my plan is not up to 15Mbps, as that is currently what Verizon is offering as their cheapest plan. It is possible I was not automatically upgraded at some point.