I've been testing Facebook's new design for months now and one thing I've noticed is their emphasis on the user's status. When logged in and looking at your profile, it's the first thing that jumps out at you.
I love the status updates because I can easily keep up with my friends without actively contacting them. I've been slowly building my Twitter audience, but most of my college friends have no idea what Twitter is. Most of my friends who have graduated from college still login to Facebook just to update their status, so it's nice that they are putting it right up front.
The latest iteration of News Feed includes a status updates tab:
And while you are chatting with a friend and they update their status, it interrupts the chat:
Is this a Twitter killer? Not yet, but Facebook is doing a great job of integrating the whole Twitter idea as just a simple feature.