I have a pair of TP-Link TL_PA211KIt 200Mbps Powerline adapters. One is plugged directly into the wall, the other is on the end of an 8 meter extension lead.
It did some tests moving a 790mb file using the Powerlines and then a direct connection using a long Ethernet cable, repeating each four times. The results were:
With the Powerlines, it took on average just over 10mins, 1.3Mbps.
With the Ethernet cable, it averaged just over 7.5mins, 1.7Mbps.
So there's a fair difference when copying files over a network, but it's still fast enough watch iPlayer in HD (not particularly fast broadband here anyway).
Would 500Mbps Powerlines be faster in this instance, or will my router, Technicolor TG582n, restrict the speed anyway?