They should have also used a red or green dot to let you know if there are apps ready to be updated.
So there's this whole new slide-up tray so you can perform tasks without leaving an app, like calculate something or take a photo or your wi-fi on or off. Umm... why isn't there a phone button?
P.S. My experience with the Macintosh operating system has a gap between 6.0.8 and 10.8 (Mountain Lion). I have to say that Mavericks is so much better than Mountain Lion. While I was just getting used to the dual monitor oddities with spaces, things are so much better in Mavericks. Kudos, Apple.