These are really great devices... but not for everybody. Most modern houses use multiple circuits for mains power, which usually splits rooms up into zones. So the ability to network two rooms requires they be on the same circuit/zone. If not, you will have to find another solution. But for everybody else, it's a win.
If you plug this in a hotel for example and there are around 50 people using the same adapter is it possible they can see your computer without a firewall (assuming the same subnet)? Or this works like a wifi router and you need to join to a network? I assume everyone will share the 500Mbps bandwidth. Is there a limit of the distance you can connect to (let say on a different building but the same grid)?
Nope. This is for connecting your devices in other rooms to your router/switch, so that you don't have to pull ethernet cable all over the house. It won't give you internet magically from some unknown place. You may ask, why not use wireless instead? Powerline ethernet is generally more stable with little fluctuate in speeds and no drop outs.
Also, regarding the multiple circuits, these new ones definitely work (albeit at a slower speed). My Netgear XAVB2001 gives me 8MB/s (~64mbps) on the same phase and 2.1 MB/s on a different circuit.
If you plug into a hotel room and I assume you have two.. others shouldn't be accessing it if you turned encryption on. If encryption is not turned on, you still have a limit of adapters that can communicate.. limit is 16.
About time, be24, who were first to launch adsl2+ tested this type of connection at least 4 years ago. They managed to maintain 1gbs in a whole office block. I heard about it from a friend and he also told me it trial was given to a handful of businesses in London. Been waiting for it ever since, but all major isps choose to milk the market dry!
I'm not sure I understand this device entirely yet. Do you receive two in a package? If thats the case then I assume you use one to your router and then another one somewhere else in the house? If thats wrong correct me please. Thanks.