Today I dropped my static IP addresses (after running numerous tests to make sure everything I did would work without them) and also had a support tech put my SMCD3G-CCR into true bridge mode (yes they will do it if you get a CSR who knows how). Now I have real native IPv4/IPv6 dual stack connectivity instead of having to use a 6to4 tunnel.
Had I initially known that Comcast allowed up to 5 simultaneous dynamic IPv4 addresses on a business class account (and that they would put the SMCD3G into true bridge mode), I probably would have never bothered to get a static IP block.