I read through some of the comments and had a chuckle...there are people complaining that 44khz audio isn't high enough quality, that YouTube needs to support 96khz, 32-bit audio...what are these people smoking??
I find it a bit strange that YouTube is moving to 1080p when their system doesn't seem to be able to handle 720p that well - more than ever now I see buffering problems, "Video Not Available" problems, comments not posting problems, etc. YouTube as a site has a lot of stability and reliability problems - and they want to add MORE strain on their server farm? Pretty strange.
It's too bad they don't allow video producers to swap out their own videos - I'd happily upload the 1080p versions of my videos to replace the 720p versions. I understand why they don't allow it though, it would be all too easy for one of those 10 million+ views viral videos to get a commercialized video swapped into its place...