My project is a tiny box in the living room that copies Blu-ray discs over NFS to a multi-TB fileserver. The difference between 100Mbps and 1Gbps when copying a 40GB image is 55 min vs. 5 min...

I should add that with DMA and checksum offloading, even a (relatively) slow CPU can handle 1Gbps data transmission rate easily.

brigade: thanks for the board tips!