My son watches a lot of Starcraft tournaments on Twitch and his immediate response was that YouTube might actually improve the infrastructure so that they could handle streaming to everyone who wants to watch.
Maybe it's just me, but I associate YouTube video with buffering, overcompression, and popups.
You can disable annotations (popups) on your Account Playback settings page[1]. Typically I have little problem with buffering or low quality unless I'm sharing the connection, but you can adjust the default quality settings on that page too.