The site has gotten a massive redesign and several new features
The new YouTube has been rolled out to everyone. The revamped site has been in testing for a couple of months and it's now ready for a wider release. The site has been completely redesigned, though it's the visual aspects that have seen the most changes.You'll notice that every section has gotten a new look and some layout tweaks. Overall, it's a cleaner look and the site feels snappier as well.
The new design is very much inspired and in sync with the "new Google look" as best exemplified by Google+ and even the search engine. It's the version of YouTube that has looked the most like other Google products and that's not necessarily a bad thing.
The homepage has gotten some small tweaks, video thumbnails are bigger for example, but the changes are minimal, YouTube had already made most of the changes it wanted to it.
The video page is another story, the video is getting an even bigger emphasis than before. The title, byline and any info that used to sit on top of the video box has now been pushed down.
Especially in the extended view, you'll know what's the most important part of the site at first glance. The most jarring change for most people is the title now sitting below the video. It makes sense though, all of the video info is now grouped together.
Playlists have gotten a much-needed revamp. The feature was one of YouTube's weak spots, the redesigned version is a big improvement.
The playlist controls as the playlist itself are now attached to the video player, a much more intuitive placement. Anyone listening to music or playlists in general will appreciate the new version.
There's still plenty that YouTube could do to optimize this type of back-to-back watching/listening, but it's a step in the right direction.
Another big addition is the YouTube Guide, a new feature that you'll see following you around on every page from now on.
The guide is essentially the left sidebar from the homepage, it's an easy way to go to any of the channels you subscribe to, see "watch later" videos and so on.
It's designed to make you spend more time on the site and make it easy to find new stuff to watch. It's probably going to do that too.