In Mavericks, some of those notification bubbles aren’t just the Mac’s way of speaking to you; they’re interactive. That’s particularly handy when the bubble represents an incoming iMessage, FaceTime call, or email—because you can now reply to them. See Figure 10-1.
Figure 10-1. Top: Whenever possible, OS X tries to get your attention using these subtle, upper-right-corner notifications. Middle: In Mavericks, some of these notification bubbles offer Reply buttons. If it’s an incoming instant message, you can hit Reply and then type your response right in the bubble. If it’s a FaceTime call, you can answer it or decline it. Bottom: If it’s an email message, you can click Reply; an outgoing, floating email message window opens, already addressed, already set up as a response. Just type your reply and hit Send. Or you can hit Delete, if you know already that the message know won’t be worth your time.)