I ran into network bottle necks on my 100base.
Wife streaming HD while I was playing games/listening to music(files on another computer).
Gigabit was a nice addition.
Save some Change and get the SMC 8 port switc, I have two
If you have a Linksys WRT54G router you may want to check out Tomato as a OS for it, mine has been unbelieveable since I made the switch.