A week ago, I reported that YouTube tests a new border based on Cosmic Panda. The most important attribute is the redesigned homepage that helps you find new channels and explore the videos from your subscriptions. YouTube started to post extra information about the new interface and it's now obvious that it will replace existing UI in the near future (the link only works after you've enabled the new interface).
"We've given YouTube a refresh. When you log in, you'll be greeted with fresh activity from your subscriptions. You can also browse and add new Channels to your homepage. Connect with Google+ and Face book to share your favorites with friends. There's plenty to discover, so login and give it a spin."
There's also an article about the new border for channels.
This new look and feel makes it easier for viewers to find and observe content. It also makes it easier for Channel creators to systematize and showcase exactly what they want. We incorporated your Feedback from the "Cosmic Panda" Channels and Watch experiment, and are eager to present:
* A more streamlined and consistent design
* An easier way to find and view videos
* New, more flexible layouts for featured content, and
* A way to keep your audience engaged even when you don't have new uploads
It's interesting to observe that the new homepage and the new channels are built around feed views and activity streaming to make YouTube even more social.
The new channels are less customizable: you can only choose an avatar, a background image, a background color and a template (creator, blogger, network, everything).
Update: The new interface is accessible for everyone.