I bought a Chromecast a few months ago, but I wish I had bought one ages ago.
Most of the stuff I watch is streamed from the internet and I previously used a combination of my YouView box and my laptop plugged into my telly. The YouView box has quite a slow user interface and is a bit clunky and plugging in the laptop (and then controlling it) was a bit of a pain.
I now use my Chromecast from my Android phone and tablet for iPlayer, Netflix, NowTV, Blinkbox and YouTube, which all have Android apps with Chromecast support (i.e. the streaming goes directly to the telly not via your phone/tablet so your phone/tablet just becomes a remote control).
The picture quality is as good as an HDMI-connected laptop and controlling playback is really easy (except for the NowTV app, which can be a bit buggy).
You can cast the entire screen of your phone which is fun when you bring your phone's camera app up - you get live pictures broadcast from your phone's camera to your telly. You can also cast Chrome browser tabs, which can sometimes be useful.
My only complaint is some lack of support. 4OD is the most annoying omission for me. Also, Blinkbox works from my Android tablet, but not from my Android phone (it's not just me - Blinkbox state that this is the case).
My Chromecast seems stable - I don't think it has ever crashed or been restarted. I only have used it from Android and the Mac OS version of the Chrome browser. I don't know if it works as well from iOS or Windows.