Wow, I feel like I threw gas on the fire and ran away.

Sorry about that.
If your computer has a gigabit nic and is connected to a gigabit switch, you effectively have a gigabit pipe to that computer. Even if everything else connected to the switch is 100Mbit, you will still get the benefit. For example, if you have two 100Mbit devices transmitting at full bandwidth to your computer through a gigabit switch, then your computer will be receiving 200Mbit/sec. If everything was on a 100Mbit network, then you would be limited to 100Mbit maximum bandwidth to your computer. Having a 100Mbit router is not a problem because I don't know of anyone who has that kind of internet bandwidth. A gigabit connection to the router would be wasted in this case. I know this is clear as mud, but hopefully it helped a little.
Aloha,
Mike