I've got it and I've managed to get it sorted and casting - cheers for the Ctrl+O trick - hadn't thought of that!
Iplayer works and Youtube works, plus casting from Chrome. If using the PC then whatever is on that tab is shown on the tv - so you could use it as a glorified monitor (not entirely sure why though!).
Plugged it in, downloaded the app and it found the Chromecast and got it hooked up to my broadband, then it kind of just works...good bit of kit but I've absolutely no idea how to use it other than a means to show what is on my PC or phone on a bigger screen.
What else is it meant to do? How do you access it to see what is on the actual device (if anything)?