I would love to have inShort in the cloud so that I can have all my diagrams on both my iPhone and my iPad. I think iCloud provides such a functionality.
And Dropbox integration would be good as well. I just don't know how. Of course I would love to able to print diagrams to PDF and save them in my Dropbox because I work a lot with it as a "Printbox", saving paper along the way. But I have a hard time thinking of a way to collaborate on diagrams using Dropbox, or even synchronizing files with multiple devices with it.