I just upgraded my LAN to gigabit. This is what netperf has to say about things.

Before:

marcus@lt:~$ netperf -H 192.168.1.1
TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.1.1 (192.168.1.1) 
port 0 AF_INET : demo
Recv   Send    Send                          
Socket Socket  Message  Elapsed              
Size   Size    Size     Time     Throughput  
bytes  bytes   bytes    secs.    10^6bits/sec  

 87380  16384  16384    10.02      94.13   

After:

marcus@lt:~$ netperf -H 192.168.1.1
TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.1.1 (192.168.1.1) port 0 AF_INET : demo
Recv   Send    Send                          
Socket Socket  Message  Elapsed              
Size   Size    Size     Time     Throughput  
bytes  bytes   bytes    secs.    10^6bits/sec  

 87380  16384  16384    10.01     339.15   

Only 340 Mbps? What's up with that?

Background info: I'm connecting through a gigabit switch to a sheevaplug. I have Cat5e wiring in the walls and the run is maybe 30 feet. If you're not familiar with netperf, it has a tendency to give very stable results and never lie.