YouTube has been testing page design upgrades and last week added
a highlights view for comments that summarizes top rated comments, uploader comments and responses that can be drilled into for more detail. YouTube also made some improvements to their new like/dislike ratings system. You'll need to opt-in to be part of the test of these new features.
Here's a good video overview of the upgrades recorded by someone who appears to either be on speed or trying to finish really quickly so he can take a bathroom break.
YouTube also recently added features so users can share videos to Twitter, Facebook or Google Reader., as well as, Facebook Connect.