I think you mean gigaBIT lan as a gigabyte lan would be absolutely insane...all it is is a faster LAN and instead of transferring at 100Mbits (12.5 Megs a Sec) it does it at 125 megabytes...
Wow that is a lot though for some reason I don't think that HDs transfer anywhere near that speed. It seems something that is more of a novelty and used for bragging rights in anything but corporate use I guess.
But if I were you considering you have a homehoffice a 100Mbit LAN should be just fine
