I particularly like the layer function. This allows for a vast degree of editability and also creative options. The masking is also great. It is especially compatible to the iPad compared to other comparable software.

It can be as advanced or as simple as you want it to be. The brushes are superb and the features like animate, palette creation and draw assist are spot on for illustrators.

Virtually no tutorials required to get drawing. I have passed my iPad over to my grandma and she was able to make art with little help.