YouTube has made a few subtle changes to how video feeds appear in subscription lists in an effort to clarify and highlight various content. Most recognizable are the larger, higher-quality thumbnails that include a bit more information, like uploader comments or the playlists a video is included in. Videos that have already been watched have whited-out thumbnails that draw less attention, but still contain the same relevant information.
If you hover over the far right of a video's entry, a small, downward facing arrow appears that will let you hide the video, bring up the uploader's recent submissions, or unsubscribe completely. YouTube is also making it easier for users to turn the content firehose back on. While the "Highlights view" will still present an automatically curated list of subscribed content, there's now a drop-down menu to see everything. The changes are live now on the default YouTube homepage for logged in users, and the product team there is also promising "more improvements in the future."