At the last CES I visited HAI's booth and they had UPB products running through the hap-hazard AC power system of the Las Vegas Convention Center show floor room.
There were extension cords and temporary transformers and just about every noise and signal sucking device you could imagine plugged into that grid (TV's, computers, etc...) and their UPB products worked flawlessly.
That one demo is why I believe UPB will remain supreme above Z-Wave and Insteon in the near future (as long as they keep their costs competitive).