I've got a combination of the Edimax HP-5103K and HP-5101ES powerline adapters and they work very nicely (at least over reasonably short distances, I can't vouch for a larger property).
The documentation they come with is pretty basic (you might say awful). Wanting to secure my network I followed the pushing the Security/Reset buttons routine as described in the instructions and everything seemed fine. A few weeks later I bought another adapter and unfortunately it connected to the network the instant I plugged it into the electrical socket - this was not good as I thought my network had been secured and therefore any new adaptor should not be able to connect without a password.
I'm still not sure what happened, perhaps I merely reset to the default password or perhaps they never secured themselves. The problem is it's hard to tell whether they are operating securely or not!
I found the most straightforward solution is the use the utility that comes with adaptors: Plug the adapter via Ethernet cable to your computer. Choose a password for the network and enter this into the "Network Name" box, check the "Set local device" checkbox and then press the "Set" button. Do this for each adaptor. They should now be in their own secure network.
The best way to test this is to try adding another adapter - it should not be able to connect to the network until the above procedure has been applied to it.
Note for those in Australia the iiNet PowerLine Adapters appear to be exactly the same thing as the Edimax AV500 Nano adapters. I've had them working together with no issues. In fact the the iiNet adapter software is slightly better, so you may like to download and try that with the Edimax adapters. This was great news as far as I was concerned as a refurbished iiNet kit can currently be picked up on eBay for $21, now that's a bargain.
