It's not really Ethernet - the devices you see are Ethernet-to-Powerline bridges. I believe, the Powerline protocol is a HomePlug standard, some designs are proprietary. Nevertheless, at least here (Europe) there is hardly any interoperability amongst the devices. The best interoperability you can get is different devices not disturbing each others communications too much.
As for the question if it's worth it - you'll see that the devices do differ in specifications - mostly the advertized data throughput varying from 14 Mbps (the early generation of the protocols) up to 200 Mbps (the current edge). The advertized data rates need to be corrected by protocol overhead and typical media properties (pretty much like WLANs) to get a number you might measure in non-laboratory environments. According to tests conducted here the newer devices typically have a better range than the older ones. All of them get into problems when operated on an extension lead or in immediate adjacency of other electric devices with a switching power supply (like computers).