I always thought that until a few people I know, including thee guy in charge of networking in our company sid they were the real deal.
I have not tested them extensively. But they are plug and play , with extra set up if you require for security stuff. They are automatically encrypted.
I have streamed dvd video files to my XBMC, as in straight vob files, off a NAS, connected to my router. Through these plug adapters both on extension leads in my house which has very dodgey wiring.
These are the ones. Really pi55es all over wireless for anything. In fact They are limited by my network which is 100Mb.
Here is the link. there are loads of different ones you can get
Linky