Thanks for the input!
I'll look into adding a zoom ability to the output or preview window, I can see how that would be handy.
When you say symmetrical spread, do you mean having the particles fire out at evenly spaced angles from each other?
I'll try and make it so that the output scale affects the preview window, shouldn't be too hard to add. :)
Undo/Redo is on the list of things to add, I'll be working on that shortly!