I use DropBox to get files on and off my iPad and for sharing documents. Just email a link to the document, instead of attaching it. I can open PDFs in iBooks or Kindle (even DropBox itself) and I just discovered CloudOn which works with your DropBox account to allow you view and edit Office documents on your iPad. So far it's pretty good. It's not as easy to use as a desktop app, but still pretty feature rich and when you need it, it's a life saver.