Its a bit clunky, but I suppose I'm used to it. For some reason Sky Go doesn't work on my Firefox browser, or Microsoft Edge, so I have to ponce about going back to Explorer. But I'm up and running in 30 secs, so no biggee.
Dunno about chromecast.
When I've wanted Sky Go on another TV though (for a bigger screen), I've just run it through my laptop, and connected it up via a HDMI cable. Straightforward enough.