John Gruber:

…one recurrent theme I see in nearly every single “how I write on the iPad” story is Dropbox. It’s the linchpin in the workflow. Scary, because Dropbox is outside Apple’s control. Scary, because if not for Dropbox, many of these people would not be using their iPads as much as they are. Scary, because Apple’s iCloud falls short of Dropbox.

Agreed. I wouldn’t be able to use my iPad a “laptop replacement” nearly as easily if not for Dropbox. But I rarely ever use the actual Dropbox app. Rather, most of the apps I use sync with my iPhone and Mac via Dropbox. Byword, Writing Kit, 1Password, TextExpander, and DropVox. Just to name a few.

Dropbox: The Linchpin