Good for sketching ideas when away from the Mac
I use OmniGraffle (pro) on the Mac, and got OmniGraffle for iOS to sketch ideas or make edits when Im away from the Mac. Its ok for that, but the lack of sync to the Mac via existing services makes editing clunky: open Dropbox (where my files usually are), action-button-open file using OmniGraffle, edit, save back to Dropbox. More than one reviewer said theyd lost work using OmniPresence, so Im not using it.
I think the iOS interface is good, once you get the concepts behind it (which are different than those behind the Mac version).
I didnt bother paying for the pro version on iOS, and a havent missed it.
G-Mo about
OmniGraffle 2