I installed two of the Netgear Powerline AV networking adapters last night and they work great. I went through and got both of the endpoints configured to use encryption. 

I'm relatively new to these, I'm curious: With sending my traffic out over my electrical wiring (Presumably encrypted now) Does the signal / info leak out over the power grid? 

I.E. could you theoretically sniff the power line for traffic if someone in your vicinity was also using Powerline ethernet?