Youtube has a playlist feature within the player?
Saw it in this blog post ;
http://googletesting.blogspot.com/2007/08/gtac-videos-now-online.html

Anyone seen this before?

Never seen it before... V Cool

This was released when they launched the Custom Player feature:
http://www.techcrunch.com/2007/07/20/youtube-launches-custom-player-feature/

I still miss the inability to customize a player for a single video...right now you can only customize it for favorites or playlists.

Not true. It's been around before that. I am not exactly sure when though.
http://www.youtube.com/blog?entry=U45UqIF2gFs (Jan. '07)

This is pretty old, but the playlist feature is pretty unknown to most people, so it's hard to discover you can actually embed a playlist.

http://www.youtube.com/view_play_list?p=8D12008293123C62