Up to this point I have relied on third-party products to work directly with my Microsoft Office documents. This past week, Microsoft made one small step toward more direct support on iOS devices: Office Mobile for Office365 Subscribers. While this app itself is free, You must have a subscription to Microsoft’s Office 365 service for this to be of use.
On my iPhone 5, can open, view and do basic edits and manipulation of the basic file formats.
This product, strangely but not surprisingly, does not (yet) support the iPad or Android devices.