That's because AirPlay mirroring solves the question I'm most often asked: how do I stream any Web video from a laptop directly to your TV, wirelessly? With an Apple TV and a Mac running Mountain Lion that supports AirPlay mirroring (check Apple's Web site to see if your Mac is compatible), anything you can see on your computer's screen -- including Flash video and free Hulu content -- you can stream to your TV.
How easy is it?
The basic process of getting AirPlay mirroring working is simple. Once you have an Apple TV and Mountain Lion-equipped Mac on the same network, an AirPlay icon will display at the top menu bar. Turn on AirPlay mirroring and your desktop will be displayed on your TV -- that's it.
You may run into some quirks, depending on the settings on your laptop and your TV. In my first run through, audio would only play through my laptop, so I had go into System Preferences, then Sound, and set the output to the Apple TV. (Apparently this hasn't been the case for everyone.)
Furthermore, to get videos to display full-screen on my TV without black bars, I had to tweak a few settings. In the AirPlay settings, "Match Desktop Size To" should be set to Apple TV. And in Display preferences, choose "Best for AirPlay" and uncheck the box that says "Overscan correction." That should give you proper full-screen playback, if you're using "pixel-by-pixel" or "screen fit" mode on your TV.
What can I watch?
The short answer is anything you can watch on your computer. The more pertinent question is what's worth watching. There's no use streaming content that's already available on the Apple TV, such as Netflix and MLB.TV, since those services are easy to use without messing with a separate computer.
Hulu's free content is a major draw, as well as the full-episode content that many major networks provide on their own Web sites. And HBO Go subscribers will finally be able to watch their content through the Apple TV via AirPlay mirroring.
How does it look?
As always, performance is going to be heavily dependent on both your broadband connection and your home network. In our lab conditions, video performance was good, although it's heavily dependent on the source. Free content from Hulu looked pretty good at the highest-quality settings, while the first episode of "Breaking Bad" on AMC looked considerably worse.
The vast majority of content falls under the umbrella of "watchable"; it's not as good as HD Netflix content and there's certainly eye candy, but it's not so bad you don't want to watch. Lackluster source quality isn't AirPlay mirroring's fault, but be forewarned that not all Web content looks great blown up on your TV.
So what's the big deal?
AirPlay mirroring isn't the first solution to this problem, but it's the best I've seen. and tried to do the same thing, but they each had their own set of problems: difficult setup, limited adoption, and pricey accessories. And while you can already do this with any old laptop and an HDMI cable running your TV, AirPlay's wireless implementation is a much better experience.
AirPlay screen mirroring has also been available on newer iPhones and iPads for some time, but many of the best apps (such as HBO Go) have blocked video streaming. And those iOS devices don't support Flash video. On the Mac, both of those restrictions go away.
I'll be spending more time with AirPlay mirroring over the next few days and updating CNET's Apple TV review, but my impression is that AirPlay mirroring is another killer feature for anyone invested in Apple's ecosystem. And it's likely to become one of the most important tools for cord-cutters looking to ditch cable in favor of free content on the Web.