The new, overly simplistic black install screen is just an overlay of the old installer screen, for now at least. When I was updating, the old screen flashed for a split-second until it was replaced with the new black one. I pressed a ton of key combinations in an effort to get to the old screen, but without luck.
About this Mac again shows "OS X Yosemite", will probably go away after a reboot.
iTunes icon is the same old one btw.
Edit: Safari seems a lot less buggy, especially regarding pinned tabs.