I don't have gigabit, but 100mb. I performed this test 3 times,,,,
I used AnalogX Netstat Live as my monitor for data transfer and windows task manager for network utilization.
The test - copying 1gb of data from another pc on my lan to my pc. Both pc's have their nic pinned at 100mb/full duplex and use QOS.
The results - Netstat Live average incoming - ~7megabytes/sec and on average for windows task manager/networking utilization was ~50-60 percent.
You can make your own conclusion,,,
Hope this helps