I have a chromecast and I can see its quite handy when you want to watch something on your tv instead of your phone or tablet. Plus it has an 'Add to TV Queue' feature when using youtube, so you just sit back go through your subscriptions and keep adding them the tv queue, then wait and watch them on your TV.
Another added benefit is that you can cast a chrome browser tab to your TV, it's buggy as hell, but helpful when you want to have a certain page with 'ticker data' or 'live graph' always visible on your TV as you use your PC for other stuff. Thats pretty much all I use it for.
I'd say for the $50 I spent, its worth it.
My 2c.