Complications

All the units came with software, the chief purpose of which was to change the encryption passwords of the adapters. The HomePlug units use 128-bit Advanced Encryption Standard encryption, and the UPA unit used Triple Data Encryption Standard encryption, with 168 bits. Either would make the CIA proud.

The main reason for encryption is for situations where other people in your neighborhood are using powerline adapters, because every house connected to the same power company transformer is basically on the same circuit. (In the US, the average is five homes per transformer.)

Some of the software modules also let you scan the network, identify all the adapters and see what speed they were maintaining. But unless privacy was an issue, there was really no reason to even load the software.

In actual use, the main drawback I found with the devices was that they took up scarce power outlets -- they didn't have through-plugs. On the other hand, they did work fine with power strips and extension cords, although the instructions warned against trying to plug them into uninterruptible power supplies or surge protectors, either of which would make hash of the signal.

Read an overview of powerline adapters here