After using my Chromecast for a month or so, and hearing reviews from a friend who has also been using one, the verdict is in: it's a hit.
Simply put, the $35 price-point and the capabilities right out of the box make the device immediately worth it. I rarely experience any issues and the quality is perfect 1080p HDMI. I have "casted" Netflix movies and a Google Play song, but mostly use it to view YouTube content. The ability to control the Chromecast from any network-connected device is a huge deal and makes it very easy use.
Google has issued 2 software updates that have helped with speed and closing a 3rd party app exploit. It still only supports the same 3 apps, but it has been officially announced that HBO Go and Hulu+ will be added soon. The ability to do the initial configuration is also now available on iOS devices instead of just Android and Chrome browser.
Chromecasts were unavailable for several weeks, but are now back on Google Play with a 2-3 week ship time.