More than anything else there needs to be an open source alternative to OneNote. Ironically, it's always been the least popular Office app and the most likely to be supplanted by an open source file format. Once tablets finally become mainstream I believe OneNote will be the most important in the Office suite. OneNote has the potential to replace paper; it'll be the default note taking app for students! It frustrates me no end that we don't yet have a digital replacement for a moleskin notebook.
http://mobileopportunity.blogspot.com/2006/05/desperately-se...
(Google should have staked out a spot in this inchoate note scene when they introduced pen support in ICS, and Samsung launched the Galaxy Note, but stock Android doesn't even have a bundled Notes app much less something to compete with OneNote)
Open source alternatives use standard formats, so it's really better than xls/doc files, for short and, above all, long term.