You can now quickly update your playlists with new videos in the YouTube's embeddable player.
Sign in to your YouTube account, then click the arrow next to the "plus" button and you can add the video to one of your playlists. You can't create new playlists from the player and you can only see the first 10-15 playlists, depending on the player's height.
It's surprising that the embeddable player doesn't have like/dislike buttons and you have to go to YouTube's video page for such a simple action.
Also, there's a contextual menu that lets you copy the video's URL and the embedding code, but YouTube uses the old Flash-only code.