I was going to make an impulse buy on this, just because after the Netflix discount (even for existing customers like me) it was going to be like $13 after tax. Couldn't find one at my local Best Buy, though, and the Netflix discount seems to be gone now, so for $35 + tax, any appeal it had is pretty much gone for me. I'm not sure what I would have done with it, anyway, since I already have a few ATV2/ATV3's, and this doesn't do anything *more* than those.
I think it's great that the Android community finally has something inexpensive and officially sanctioned by Google which offers AirPlay-like functionality. As has been detailed by others, it's not really using the same methodology as AirPlay, but it does provide the same end-result for certain things.
I'll add that for some of those types of things, the methodology it uses is superior to Apple's AirPlay implementation. For example, if I want to find a TV show to watch using the Netflix app on my iPhone and decide to start it up and beam it to my Apple TV, I'd prefer for the Apple TV to take over all of the heavy lifting and fetch the show itself, and have my iPhone just become an [optional] remote control for pausing, etc. Instead, Apple's implementation results in my iPhone doing the heavy lifting of streaming the show and decoding it (and sucking down battery life) and then pushing it over my home network to my Apple TV (resulting in additional network hops that could result in playback interruptions). In fact, the Google Chromecast methodology is pretty much exactly what I recommended long ago should have been Apple's approach for these use cases.
Now, for other use cases (e.g., showing off the photos/videos stored on my iPhone, or doing a PowerPoint presentation from an iPad or laptop), the Apple AirPlay methodology is superior. Then there are use cases for a dual-screen approach (e.g., playing a game where the iPhone becomes a custom game controller and the game itself is displayed on the TV) which, again, the Apple TV is capable of doing, and this Chromecast device may never be capable of.
I should note on that last point, that the Chromecast, like an ATV/iPhone does contain a little computer of its own inside. I'm not knowledgeable about the CPU/GPU specs, RAM, onboard storage, etc., so I don't know to what extent it can/cannot be improved via firmware updates. I suspect that it's less capable than an ATV3, though. I base this opinion largely on the price they're offering it at.
Circling back to Apple's approach...even for some of the functionality that it's capable of (mirroring your screen), it's not without its limitations. Specifically, lagginess/delays. If I mirror my MacBook screen, there's an obvious lag between the mouse pointer moving on my laptop and seeing the mouse pointer move on my TV. Again, this is likely due primarily to the multiple network hops going on. This is why a lot of folks have expressed a desire for WiFi direct. I think that will require new iOS hardware, though (both a new ATV hardware revision and a new generation of iPhone).
The new support for Bluetooth gaming controllers in iOS7 may also, hopefully, address lag issues for gaming, but it would still seem to me that to fully address that, they also need to incorporate another recommendation I've made in the past: storing the app (or some portion of it) directly on the ATV itself. Unlike a lot of people clamoring for "apps on the ATV", though, my vision is a little different. I'm envisioning a platform where the iPhone or iPad is still your "hub" where all of your apps are stored. But if you want to play a game or use some other 3rd party video app, and stream it to your TV, what happens is the app (or some portion of it) gets transferred to the ATV, so that the ATV can do most of the heavy lifting. The iPhone/iPad then become the controller. When you're done using the app, the ATV may still cache the app code for some period of time. That way, if you go to use the same app again soon thereafter, it doesn't need to take the extra time to re-transfer the app code from your iPhone to the ATV again every time. Perhaps 1GB of storage gets dedicated to the app cache, so whenever it fills up, it starts deleting the oldest used apps/data.
Anyway, at this point, I'm still optimistic that Apple will continue to improve the ATV. The more than can improve using the current hardware platform, so as to maintain backward compatibility, the better. But at $99/box, I'm not opposed to ditching some/all of my current ATV's if there's some important improvements they want to make that require new hardware.