This does pretty much exactly what it promises, giving you effectively three ethernet ports from any mains socket in your house, and I use it to connect my printserver, PC and network storage.
However, if you are running any PC game through this that is sensitive to latency problems, you will find it annoying and frustrating. I got about the same through this as I did with a direct wireless connection (200ms), so for the PC I swapped it for an individual device with just one port. That reduced the latency to around 100-140ms. Still not great, but the connection is at least reliable.