I use this software primarily for my webcomic and quick layer edits while on the move (ipad). I personally think it is excellent, and suits my need perfectly.

I have a list of features/improvements I’d like…

1 - Option turn off the post-filter. sometimes we like the jagged edges left on.
2 - Duplicating a layer degrades its quality, like it gets post-filtered twice. This needs to be fixed!
3 - Ability to import another sketch as a single layer.
4 - Ability to save pre-defined color palettes and quick switch between saved palettes.
5 - Ability to paintbucket “delete”, for erasing large sections of a single color.
6 - Ability to export the whole sketchbook in a single go. I don’t trust itunes backup and would like to be able to periodically export all my hundreds of sketches to PSD.
7 - When moving a layer, all layers lose their multiply/add/screen properties during the move process. I understand this was probably done for performance issues, but it would be nice to switch that on or off.
8 - There is a massive difference in size between a brush that is 1.1 and 1.0. Why?
9 - Paintbucket fills do not antialias correctly against the edges of other colors. Sometimes there is a band of lighter color at the edge.