Wireless range extenders, any good?

I get a call from my friend and she tells me that her wireless router "blew up" so she bought a new one at Walmart. Unable to get online, so can I come over. I get to her house and she was sold a range extender instead of a wireless router. Exchanged it for the right item and now she can get online.

My question is, do the range extenders work? The one she was sold has ethernet ports so you can convert wireless into wired.
I have a cousin with wireless issues in his house and the extender might do the trick.

Yes Off Course .. Range extenders or Access Points can work if you a have router at one place and you want to extend the area of coverage of the Wifi signals. Its important to get at least very good or excellent signal in Wifi for you to get good internet speed.