well... I'm using illustrator since Illustrator 5... not CS5!! Illustrator 5!!! About layers... Layers must be one of my most used part of Illustrator. If you do a loot of illustrations, layers is a must!, I know you can lock part of your artwork, but moving part of your design to a different layer, locking the layers you don't want to touch, and then locking and unlocking parts of the design you are working on in a different layer gives you a really powerful workflow. Layers can be used as different pages too, I know in Designer you can create pages now, but compared to illustrator is a little bit messy right now. I prefer to handle this with layers (in Designer) and I even found a script for illustrator that you can export every layer as a PNG, if you work with After Effect or any other animation software and you need your design in parts, this makes things really easy!!