RobertB
I don't know that the technology is perfect, but it's a least viable.

I've used the Netgear divices for years because I did not wish to make the effort of running live cable upstairs. Turned out to be a very satisfactory, simple, and easily implemented solution. Note that the electrical wire may affect how fast the speeds are, although I do not know the physics behind that. I would assume newer built homes may experience more optimal speeds (better wire???). I get around 5Mbps which is adequate for my needs.

Another option not to forget is when you wish to have a wireless connection, but the location is too far from the main wireless router. You can add a wireless repeater, where the repeater is located within the range of the main router, and subsequently within the range of the new wireless connection devices. In my case, I have one hard-wired connection upstairs, so I added the repeater to that line. Now all upstairs rooms can connect wirelessly, whereas before some rooms were beyond the wireless range.