In a track, you may have, let's say, 6 Layers (six takes). There are many times, due to various reasons, I'd like to move a selection or audio event to another Layer or another place on the timeline in the same or another layer quickly. There are also times I'd like to double up two audio events in two different Layers to play simultaneously (like a doubled lead vocal), without having to create a whole new track and copy audio over manually.
To compare with Sonar: In Sonar, you can select and drag an audio clip from any Take Lane (Layer) to literally anywhere else in the DAW project (song). You can also highlight a group of clips and move them all at once. Editing is really easy and fast with this ability. Sonar also offers the keystroke "K" to mute/unmute a clip in a Lane/Layer at your whim. This is also very handy for a vocalist who likes to overlap words in a comp.
To add: It would be nice to allow editing in Layers vs. just the track. I can drastically clean up the Layers' appearance, since I'm big on having a truly clean Song.