YouTube went offline last night for updating. The new version is live now. Features include the capability to customize the colors and content on your personal profile page, and a new Google Labs-like feature, TestTube, where you can experiment with new YouTube features. The TestTube projects are the interesting thing here.
For example, TestTube has the new Audio Swap feature (previous coverage), which lets you replace your video's audio with a music track from one of several artists that YouTube has made arrangements with. The interface to make the swap is easy, and the selection of musical themes is pretty good. This isn't where you'll find millions of tracks by famous artists, but for making your talkie into a musical, there are decent options. Once you make the audio swap, the artist is supposed to get a credit on your video, but I didn't see anything to that effect in my testing.
The major snag with this feature is that it completely overwrites your video's audio track. There's no way to fade the music in our out or to duck it under voice. For that, you'd need a more full-featured video editor, which Google/YouTube doesn't yet offer. (See JumpCut -- but, wait, that's a Yahoo product now. Oh well.)
Also new: Streams. These are fancy video channels with chat rooms attached. Users can add videos to a stream (that the stream moderator can later remove) and chat about what they're watching. It's a nice swipe at adding some real-time interactivity to YouTube, but I did find the chat window hard to follow--when there are a lot of chat messages flying by, it's hard to tell which videos in a channel are being talked about, despite the little video preview thumbnails that are attached to each message. There are some other snags in the system: I couldn't switch videos in a stream easily. That's why the feature is still in the test kitchen, I suppose.
Lycos and Stickam also have video-based chat rooms, but YouTube's Streams should ultimately be better, because it's so easy to add a video from the enormous YouTube library to a stream, and then begin chatting about it. Streams could become a very fun place to hang out online.