A bit over a year ago, I tried Powerline Ethernet with not particularly stellar results. Today, however, I found another set at a yard sale: a WD "Livewire" kit, that I only looked at because they had integrated 4-port switches at each end, and on a cursory google search I thought there's a chance they might be gigabit (the link between them is up to 200mbps).
I asked how much and they said five bucks, for that much I figured I could take a gamble, and it turned out I lost, but still, it was worth a shot. I needed another switch for behind the TV, and fast ethernet is acceptable there at least, so I plugged one in and forgot about it.
A little while later I decided to give the other one a shot, and to my surprise, it synced all the way from the office to behind the TV - the complete length of my house. Were the last two kits I tried just defective? It seems unlikely, but who knows. Maybe this kit is just really good.
Decided to fire up
iperf3 and the results were pretty great considering it's travelling the length of the house, with no attention paid to ensuring it's on the same circuit:
[ 5] 0.0-10.3 sec 50.6 MBytes 41.3 Mbits/sec
I dunno if I'll use them, but it's nice to know they work!