I don't usually watch Youtube, but when I do, I prefer...to just use a plugin to download the videos to local storage, watch them, then delete.
If you're a moderate to heavy Youtube user, this is probably too annoying, but if there's only a few videos/channels you're interested in, queue up each video, download it, and watch them all without interruption when they're done. I use this Firefox plugin: »
addons.mozilla.org/en-US ··· dio-dow/ . It's very easy to download videos in just a couple clicks.
If you want 1080p, you can get that too with that plugin, but Youtube doesn't make it hassle free. Youtube splits 1080p video and audio into 2 files, so you have to remux them into one. You need ffmpeg for that, and you can even link ffmpeg to that plugin and it will do the remux for you. I prefer to do it by hand (well, with a python script). Also, if you really want the best quality and have bandwidth to spare, download both the 1080p video and the 720p file (which contains both an audio and video stream), extract the audio from the 720p file, and mux that with the 1080p video. The reason is that the plugin reports that the 1080p audio stream file is actually at a lesser bitrate than the stream in the 720p file, but the difference is minimal.
Plus, sometimes I find that your OS's player renders better than the Flash player.
