Yeah, that's what I do. It's easy and works with almost every app, because almost every app that creates new documents has a "send by email" button somewhere.
I set up a special Gmail account to use just for this. Essentially the inbox of this account is just a big cloud-based iPad document container.
I really like Dropbox, but in order to transfer your files back the application has to be written to use it, and unfortunately the Apple iWork apps are not.