I especially like how the video plays in the header while rest of the page selection remains the same. This way, I can go back and play my #2 choice after my #1 choice has finished without having to look for it, I already know where the #2 choice is.

Youtube is horrible at this. If you don't make a playlist, you have to click back and hope it still recommends the same videos as the last time you were on that page.