This is new tech based on an old concept, there is a difference between the two. The new part is that it is running at 200Mbit through the internal power-lines and using an encrypted point to point tunneled connection between your router / gateway and the access point. For small houses or simple network layouts this is unnecessary as your Linksys / D-Link router + access point device is all you'll need, but for larger multifloor houses this is a god send. Have the internet gateway device + access point (not always the same thing) down in the office or network closet (if you have one) then use one of the Trendnets to create another access point upstairs and / or at the other side of the house. I would like to know if multiple power-line access points can run off the same gateway-side adapter, then you could use a single adapter to run 2~3 different power-line access points to reach upstairs / basement / porch outside and so forth, all running at 200Mbps (assuming clean internal power).
You ~could~ try to use WDS to chain the wireless access-points together but then you run into some serious problems. First being that WDS transmissions are done at layer 2 and will draw from the same bandwidth pool available to the clients. It effectively halves your available bandwidth as each broadcast from one side much be repeated to the other. The next problem with WDS is that it must be in-range of the next AP, and the signal must be strong so they have to be relatively close to each other. This would restrict the locations you could drop WDS repeaters and you would be forced to use a whole lot more of them scattered throughout the house. Honestly WDS really isn't good for internal housing, its more of a distributed network concept. The best implementation of WDS I saw was when a friend of mine used a WRT-54G v3.0, flashed DD-WRT to it and connected two customized parabolic antennas. Using WDS he was able to get a clean signal at over 500 meters on one side and repeat that signal to another system at 200+ meters along with providing a seamless connection to his internal network.
In short, this power-line AP seems preferable to extending network service across a house that has many dead spots and concrete walls along with multiple floors. It does the back-end connection across the power-line which leaves the wireless bandwidth open for device use and bypass's wireless restrictions.