Here are some quick instructions if you would like to grab high resolution copies of all of the videos in a YouTube playlist.

Install dependencies (replace brew with apt-get or yum for linux):

$ brew install youtube-dl ffmpeg

You can get a muxed 1080P version of all videos in a playlist by running the following command and replacing the URL:

$ youtube-dl -w --restrict-filenames -f 137+140 -o '~/%(playlist_title)s/%(upload_date)s.%(ext)s'

The -w option will disable overwrites, and --restrict-filenames will make the saved filenames URL safe. The -f 137+140 option tells youtube-dl to grab the 1080P video and AAC audio files, and mux them using ffmpeg.