Is there an iPad app like Snagit for marking up screenshots or pictures with arrows, callouts, dropshadows, torn edges, etc.? I LOVE Snagit.

I know that captures can only be done in iOS with the built in Home-Power screenshot function.

But I'm looking for an app that will allow me to edit those shots and add arrows, shadows, edges, callouts, blur, freehand circles, etc.

Is there something that does this well, with a focus on annotation?  (So I get that I can do this in Keynote an other apps, but since they're not made for it, it's painful, they can't export the picture back to the photo roll, etc.)
I you are looking mainly for annotation then Skitch could be worth a look.
It lacks the more fancy features you asked for (torn edges, blur, etc.) but for basic annotation (arrows, text, freehand) it is quite good.
Although it was acquired by Evernote it is possible to save the annotated image back to the camera roll.