Some tips to make this app top of the hill!
1) Add drawing of Polylines (1 long connected line)
2) Add drawing of Cloud shapes
3) Add drawing of Arrows, or change the start/endpoint of lines (arrow, dot, circle, slash etc...)
4) Multitouch: Extra button left or right bottom, if that is continually pressed with another finger, lines only are drawn in ortho (horizontal & vertical, like Autocad)
4) Undo + Redo
5) Easier entrance to settings + please do not combine all draw settings in one menu! It is so not clear this way.
For Example press & Hold on rectangle should show a popup window just like the 'icons' button, there you can adjust only rectangle settings. That would be so much easier.
6) Windows version
7) Web version (OS independant)
8) Have to think about that...
Customer support service by UserEcho