I have used Devolo dLAN 200AVs extensively in my UK home for about five years now, and they are great.
I have about six of them, all single Ethernet port (multiport versions, which three Ethernet ports, are available). I have not found this to be a problem, because I have switches/hubs in most rooms, anyway.
They have UK plugs, not US plugs, but none of my dLAN 200 AV devices are pass though (i.e. you can plug a mains device into them), so I needed either use an extension cable with a 4 or 6 way plug board attached, or where I had dual sockets in the wall, I just sacrificed an outlet.
The benefit of pass through devices, is that they contain noise suppression circuitry inside them, to help counter any noisy devices, or power on spikes that may be generated by adjacent devices that may also be plugged in to the plug boards. Devolo actually recommend that the dLANs are not plugged in to plug boards, and that they should only be plugged in at the wall, due to signal degradation. However, I personally, have not experienced many problems, mine all work fine.
I recently added two 500 dLAN AV Plus devices, which do have pass through.
I use these for a higher speed connection from my media server, in my garage, to my lounge, where the XBMC is, and I can stream videos just fine. They also are compatible with the existing 200AVs, so now every room is connected.
They even come with a remote admin tool, the dLAN Cockpit, that works on OS X (as well as WinTel machines). Also available are Wi-Fi extenders, which act in the same way as the Ethernet variants, but pump out Wi-Fi instead.
Also, the wiring in my house is about 50 years old, and no problems have arisen because of that. They can get quite warm, but even after having them plugged in for 4 years solidly, that has not been an issue.
I can not recommend these highly enough.
Also, I purchased all of them, secondhand, on eBay for around £10 each for the 200AVs and £20 for the 500s. Just wait for someone selling a bulk lot because they are upgrading (i.e. from 200 to 500, so they are selling off the 200s cheaply).