There are several word processing apps for the iPad, ranging from Documents to Go (Premium), Quick Office HD, Pages, iWriter, and others. None of them are going to provide full laptop-replacement. Many offer syncing ability via google docs/drive, or dropbox, Pages has iCloud; most will allow a file to be emailed.
As someone who writes everyday, I simply do not see the iPad as a great replacement for a laptop when it comes to doing any serious writing. It can be done, but there are trade-offs. And any serious writing is going to demand an external keyboard, and I have to admit if I have a keyboard and a screen, I'd rather have the flexibility of an actual laptop.
But try an app, and see if it works for you.