The Windows Store has a paltry collection of productivity apps for word processing, spreadsheets, presentations, and mail. So far, only one member of the Office suite—OneNote—has shown up as a modern UI app. Other productivity suites are no-shows, too, including Google’s QuickOffice, DataViz’s Documents to Go, and LibreOffice.
We've heard whispers that productivity developers fear to tread in Office's natural stomping ground, and rumor has it that modern UI versions of the entire Office suite are indeed on the way. For now, however, if you want to get any serious work done in the modern UI, you’re better off giving Web apps a try than sampling the Windows Store.