I have had Chromecast since the day it became available.
As a fulltimer, I have enjoyed its possibilities.
All it does is "cast" whatever is on your phone/tablet/laptop to the TV screen, including audio.
It needs an HDMI port on your tv.
For power, it can use the AC adapter that comes with it, or you can plug it into the TV usb port.
To avoid streaming issues of speed and data while traveling, download the media while on a fast/home connection.
I like being able to play my phone's music library through the decent speakers on my Samsung 22" tv. Can also be used to show slideshows to friends, etc.
For $35, I've been satisfied with it.
Anything you can bring up in most browsers can be cast, and many apps are Chromecast ready.