It takes a giant leap of faith to download a preview app from a beta store to run on a technical preview of an unfinished operating system.
And yet the pent-up demand for a touch-optimized, tablet-ready version of Microsoft Office is great enough that a million or more members of the Windows Insider beta program are likely to do exactly that with the first releases of Word, Excel, and PowerPoint for Windows 10.
In an acknowledgment of market realities, the preview releases of these three core Office apps are arriving on Windows well after their counterparts on iOS and Android.
The three apps share a common look and feel and feature set across all three platforms, with a pared-down feature set designed primarily for reading, viewing, presenting, and performing light edits on smaller screens.
Because these are Windows universal apps, they'll install on any device running Windows 10, including full-sized PCs and phones. But they're clearly optimized for small tablets.
I put all three apps to the test on a Surface Pro 3 (using it mostly without the Type Cover, as a 12-inch tablet) and the 8-inch Dell Venue 8 Pro, both running the most recent preview release of Windows 10. (Because the Windows 10 phone release is not yet available, I couldn't test that scenario. But these universal apps should work on those devices when a Windows 10 preview is released for phones.)
In Microsoft's new "mobile first, cloud first" world, it's not surprising that all of the apps are designed to work with its cloud storage services: OneDrive, OneDrive for Business, and SharePoint.
The store listings for all three apps claim that they work with Dropbox as well, but I couldn't find any easy way to create a new document, spreadsheet, or presentation in Dropbox.
As in their desktop counterparts, all three apps share common tools that allow you to change text formatting, insert pictures, and create charts, using touch-friendly menus. If you open a document that contains formatting created in the desktop version of the app, features not supported in the tablet version, such as Word SmartArt, Excel sparklines, and PowerPoint animations, display properly.
Some tasks are especially well suited to use on a tablet. For example, in PowerPoint, you can connect to an external monitor wirelessly, using Miracast, then tap to advance to the next slide or press and hold to create a bright "laser pointer" to highlight items on a slide.
All of the apps contain tools for inserting, cropping, and formatting pictures, using the same set of built--in styles that are available in the desktop Office programs.
Some advanced features used by enterprise customers, such as macros, aren't supported. I wasn't able to test documents protected by Information Rights Management features.
These are definitely unfinished apps. I encountered occasional issues with file locks on Excel spreadsheets not being properly released, for example.
In theory, these Office apps are most likely to appeal to business users who are already subscribers to Office 365. At least in this release, however, the initial selection of canned document, spreadsheet, and presentation templates is skewed toward home users and students.
Heavy Word users will appreciate the support for tracking changes made when multiple people are working on the same document. As with Word on the desktop, you can view tracked changes, see the original or revised document with changes temporarily hidden, and add comments that incorporate your name and a timestamp.
All three apps include the ability to share a file as an email attachment or as a hyperlink to a shared location in OneDrive or OneDrive for Business. Documents you receive as an email attachment can be opened for viewing directly within the app.
Although it's possible to use these apps on their own to create and edit simple documents, they're clearly intended to be companions to the full desktop apps. Use Office on a full desktop PC when you need to create and edit highly formatted documents; use the tablet apps for reading and light edits.
Now that the Windows apps are available, updates to the apps should appear on all platforms (iOS, Android, or Windows) in roughly the same timeframe. It will be interesting to see whether Windows continues to lag those other platforms or whether new releases are available simultaneously.
The final versions of all three apps will be ready before the end of 2015, probably at the same time Windows 10 is released.
All three apps are available in the Windows Store (beta) app on devices running the Windows 10 Technical Preview.