my personal experience, having come across them a few times, is if possible, use something else.
their attraction in theory is 'plug and play' but in practice they can be difficult to setup and high maintenance.
I use the same philosophy with these devices as I do wifi, if possible go ethernet, but if you can't, alright give them a go.
I think Salmon is right, it depends largely on how the home is wired.
they were popular a few years ago, before the latest gen of dual and tri-band routers that have far superior coverage and penetration, elimination the need for these devices.