A Chromecast may be exactly what you need in your living room, but it's not a Google TV replacement
While many of us have our Chromecast dongle, and are happily playing with them and sending content to our televisions, there are plenty of folks who have some very valid questions about what the device is, what it can do, and especially what makes it different than a Google TV box. We can help, and we'll start with the last question. A Chromecast and a Google TV unit are very different devices.
The Chromecast is basically a gateway to content. You can't install anything to it, can't control anything on it without another device, and can't even set it up without a web browser or an Android app. There are a few hiccups with it, as should be expected with any new device (turning off hardware acceleration in Chrome is a good quick fix for some of them), but for the most part it works as advertised. It's easy to set up and use, and unlike plenty of other Google products doesn't require a 100 page instruction booklet to get things up and running.
Google TV, on the other hand, is a full-blown Android device. It has access to the official Google Play stores so you can install applications and games, rent or buy movies to play directly on your TV through the device, listen to your Google Play Music library, browse the web, and even use your network connection to use adb to communicate with it. It's pretty much just like your Android phone or tablet in these respects. You don't need another device to set it up or to use it, and with the included remote your Google TV is a complete stand-alone product.
Now there are some similarities on the surface, so we understand why there's a lot of confusion. Some people have an idea that Chromecast features will be merged into Google TV, or a few Google TV features will be merged into the Chromecast. We're not going to speculate on either, other than to say we wouldn't be surprised. Google wants in your living room, and they are willing to think outside the box to do it.