Since I've been toying with the idea of SageTV as an HD DVR, I've been thinking about converting part of my LAN to run GigE. Our house was built in 1999, before Cat-5e was standardized, so we've always had a 100 Mbps network on plain old Cat-5. We also only put in 2 runs of Cat-5 per location, so I ended up splitting the Cat-5 runs for the LAN (2 pairs for the LAN and 2 pairs that I could use for other low voltage needs). However, GigE needs all 4 pairs. As a test, I freed up 2 pairs on one of the living room runs, allowing me to have all 4 pairs in one run. I was able to link up two D-Link GigE switches over that run at gigabit speed. I put a cheapo Airlink GigE NIC in the HA server but I don't have any other GigE devices to test the throughput I can get over my wiring. I guess I'll find out when I eventually build a Sage server with a GigE NIC.
Update: I put another Airlink GigE NIC in our kids' computer and was able to get around 250 Mbps file transfers - not bad running over 10 year old Cat-5 wiring, Cat-5 jacks and a Cat-5 patch panel.
Update 3/22/09: I'm now seeing about 400 Mbps to our new media server with the same Airlink card.