When I delete a layer in AE CS5.5, is there a way I can get all the other layers above it to fall back and fill in the empty spot in the timeline, without physcially having to move them all?
Not automatically. But you can do this:
Put the timeline cursor at the point where you first layer to begin once everything's moved.
Click on the layer immediately above the layer you're going to delete.
Shift-click on the the top layer -- you've now selected all the layers above the one to be deleted.
Shift-drag the selected layers. They'll snap to the point where the timeline cursor is located.
Once you've confirmed that all is well, delete that undesired layer.
Shift-clicking on the top layer to select everything above did not work (I'm using Mac). However, using the selection tool and just dragging around all the layers
above accomplished the same thing. Then your trick worked like a charm. Thanks very much.