I really like mine so far, I have had it for almost 2 weeks. We have had a roku for a few years on the downstairs TV which we use the hell out of because we cut cable over 3 years ago. The main thing the Chromecast gives us right now is native support for youtube. There is a ton of stuff on youtube that makes that worthwhile. Most of James May's non-Top Gear shows are out there along with a bunch of movies and every episode of Discovery "Wings". The only disappointment is the lack of the cast feature in the android browser, but I assume that is coming.
One interesting note, we have a Wii on our upstairs TV. After I got the chromecast I checked their app channel and noticed the Wii has a native youtube channel now too. That little console has been worth every penny for all that it does.