Windows 7 and 2008r2 both worked fine with no settings/changes needed. My Snow Leopard partition didn't work on its own but was an easy fix. I just had to go to System Preferences > Network > Advanced and manually enter in the router's ip address (it had automatically populated the field, but it was wrong). As soon as I did that it worked great.
robinjames: In automatic mode it should have worked, unless the router advertisements aren't working properly? Gabe, can you confirm whether there are any issues with router advertisements in this firmware?
On a separate note, does TekSavvy's IPv6 offering work with Apple Airport Extreme (IPv6 capable router).