I've been a long time coming, and I'll be a long time gone. You've got your whole life to do something, and that's not very long.
|--Ani Difranco (American singer, songwriter, and guitarist)|
The timeline is After Effects' killer application. It is the reason above all others that After Effects is equally effective for motion graphics or visual effects work. Node-based compositors make it easy to see render order, but they can make coordinating the timing of events more difficult.
With the timeline, you always know how layers and their keyframes relate in time. Some would argue that render order is more significant than timing ...