I think you need a PowerBook to get gigabit on a laptop. They have ethernet to usb/firewire though, and there'll probably be gigabit soon enough. Keep in mind you don't need a gigabit card to connect to a gigabit network.
PCI bus speed is 133MB/s which should be able to support 1000Mbps (125MB/s), but that is pure bus speed. This is the reason I don't believe the SATA PCI cards actually work at 150MB/s.