I live in the ultimate problem house for PC networking: old, long single bay, town centre, complex wiring. Everything was rewired 10 years ago, through one meter, but with 2 consumer units. I wanted to set up an office in a room as far away from the wireless router as you can get and the signal wouldn't reach, so the dLan seemed like a good solution. However, with the the ethernet unit plugged into the mains near the router, I couldn't get a strong enough connection through the mains in the room where I wanted to work, or anywhere close enough to pick up the dLan's wireless signal. The connection varied enormously, even from socket to socket within the same room. I couldn't make it work, in either of the configurations the dLan supports.
In the end the solution was a 15m CAT5 cable from the router, through a hole in the wall and strung along the outside of the house, then back in at an electrical socket near the room I want to use. So the other end of the cable is plugged into the dLAN and I get now a very good wired or wireless connection in the "office", though the much shorter and simpler mains run. This saved me another 15m of internal cabling which would have been difficult to do neatly.
I bought a cheap 4-port ethernet switch, which is plugged into the dLAN, and now have 2 laptops with wired connections, which works very well. To be honest I rarely use the wireless, a wired kit would have been enough and if I was doing it now I'd go for the 200MB version.
Bottom line: I'm sure it would work more easily in a simpler environment. In a difficult situation you can still make it work with a bit of ingenuity. It does work across 2 ring mains, but performance will vary. The range of the wireless unit isn't great, wired connections are better.