If you've been me, you've been trying to make lines, sharp lines in the subsynth editor (less so in padsynth editor. But maybe you did :)) oh! Just a thought, you can use this trick in pattern auto too.
I stumbled upon this this morning, and my apologies if everyone already knows it...
If you use multi-touch you can create lines from finger to finger (put two fingers on the screen) and I also noticed that you can get interesting seated (edit: serated)edges by moving your fingers a very certain way. Experiment.
The seated (edit: serated... What's wrong with you, autocorrect?) edges aren't there at all if you do it correctly, but appear if you don't, but either way it's useful. :D
Also for square kind of shapes, dragster finger from editor to underneath editor and swipe around a little for the shape you desire (I think that one is known though!)