Best word processor: Quickoffice Pro HD
Quickoffice, owned by Google, has long been the top cross-platform mobile office productivity suite. The newest version offers tracked changes and notes in the app itself, following on Office2HD's innovation. In addition to AirPrint support, it exports your files to PDF.
Quickoffice Pro HD's strong support for cloud storage (though not iCloud), and its straightforward editing tools make it the closest thing to a native Microsoft Office for the iPad. Quickoffice makes a really good companion to Microsoft Office on your PC or Mac.