Joost is the latest creation from the guys who shook the music business with the file-sharing application Kazaa, and brought quality phone service to the Web with Skype. Their new application, in closed beta for a year but now available to the public, is a free, ad-supported, "TV-like" platform that streams video and also provides interactive tools to help you find new things to watch.

It's an undeniable leap forward for online television, an idea flirted with for years -- short videos on YouTube, high-quality downloads on iTunes -- but never realized in a way that allowed you to stream longform content similar to what you would find on TV.

But while Joost does offer some quality content -- selected shows from CBS, MTV, Comedy Central and CNN, just to name a few channels -- the platform still suffers from several major drawbacks that make it less than required viewing.

In fact, there's a simple way to determine whether Joost is worth your trouble: If you're content to surf high-quality, mainstream fare on your TV set, this application isn't for you. If, on the other hand, you're a multitasking Web video watcher who doesn't mind poor image quality, then you'll enjoy Joost.

Here's how it works: Joost launches as a full-screen application. The screen's free of visual obstructions unless you move your mouse, at which point DVD-like control options appear. The video itself is full-screen but relatively low quality (YouTube's the best comparison here), and tends to stutter from buffering, though there's never an interminable pause in the action. Joost's search box, which appears at the bottom of the screen when you move your mouse, returns relevant results, but only when the keyword matches Joost content.

There's the first big problem: Joost boasts more than 15,000 TV shows on 250 channels, but most of the programming is very niche. The biggest bill of fare is CBS' "CSI: Crime Scene Investigation," which offers a deep library of shows. MTV also offers episodes of "Punk'd," "The Hills" and "Laguna Beach."

But other channels only offer less popular shows; no "The Daily Show With Jon Stewart" or "Colbert Report" on Comedy Central, no "Anderson Cooper 360º" on CNN. The rest of the programming is a bevy of good but less well-known fare, including video from the Onion News Network and channels with such names as Australian Food TV, the Really Terrible Film Channel and Earth Talk Today.

Ads are visible while watching all the channels, but the insertion is elegant. Small ads appear on the lower-right of the screen, and sometimes as interstitial screens between programs. In most cases, you can click on the ads to be taken to an external Web site, at which point Joost minimizes to quarter-screen size.

What Joost lacks in content it tries to make up with nifty tools. For example, Joost's menus are gorgeously semitransparent, allowing you to select from a variety of channels without interrupting your video experience. While watching, you can launch an instant-messaging application that allows you to chat with other people viewing the same video. You also can invite friends to watch what you're watching, allowing you to congregate around a shared media experience.

Overall, Joost doesn't replace the television-watching experience. At best, it's an artfully realized complement.