Are the any limitations to the "power-line" or "mains electrics" type Networking devices? - power line networking

I have for this type of network device, and I was wondering what, if anything, was "contra" to operate.

- Http: / / www.scan.co.uk/Products/Linksys-By-Cisco-PLTS200-UK-PowerLine-Turbo-4-Port-Adapter-4x-10-100-to-85Mbps-Homeplug

Have you when disconnecting an electrical appliance is it? They work in each household? They are fast and more slowly when more power is connected? May connect to the 4-way adapter and surge protection?

And finally, I recommend?

Thank you, Ben.