Well I use Edge Touch on my iPhone. The only problems I've encountered in its use are due to my screen size. I'm sure it'd work much better on an iPad. Apart from that, its very simple and accessible, and gets the job done.
I've tried Sprite Something too, but I feel the interface is overly complex. That's just me.
I would recommend EDGE Touch if you just plan on making one shots, and if you get used to Sprite Something, its good for simple sheets since it already has support for sprite sheets and animations.