How to do a file app on the iPad:
Start with the concept of the photo app and apply it to all all file types. Add functionality to delete/copy/organize files.
Why a file app (system) is important:
It's stupid to think that file systems should be a thing of the past. Computing revolves around files - music, pictures, movies, homework assignments, and so on. So long as that is the case (which it surely will be for a long time), you need some method of managing and organizing them.
Despite what some may believe, iOS
does have file management. It's handled on a per-app basis and is very inefficient and has limited functionality as many posts have already described. For some type of files, it works very well, such as for music and iBooks. These types of files have standard information associated with them (subject, album, artist/author, etc.) that can organize files in a more dynamic way than folders can, so app that does that is more powerful than a generic file browser. For other file types, however, there's no such information so the same system does not work very well.
Actually my boyfriend works for Apple so he added me to his free MobileMe family account. But anyway, you can use Dropbox, which is free, in the same manner.
That's analogous to using Push for notifications that can be handled locally. It works, but it wasn't a very sensible solution (some compared it to mailing a letter to yourself), which is why Apple introduced local notifications.