Copy and pasting is essential for any layer based editing program, as it lets you break an image into several pieces that can be individually edited.
Here are some great examples of images that were made using Copy and Paste
"Bottled Fish" by Nicky666, uses the following source image, copied and pasted into new layers:
"Iggy's Night Out" by meowza, uses the following source image for both a main component and window reflections.
It's very easy to see why this functionality is the most important one to achieving photo-realistic image effects.
I'm including this here, rather than in its own post because it is a really quick and simple demonstration. Phoenix includes 20 history states, which means that you can undo/redo up to 20 steps back. We can presumably allow more than that once Flash Player 10 is released and memory usage is optimized further.
Our History Panel shows you a thumbnail (optional) of all previous states in addition to the activity done / tool used during the step, letting you visually jump between steps quickly and easily.]]