Most likely to conserve screen space, all of the formatting options are tucked into a Format bar, which you can access by hitting your device's Menu button. There are formatting options to bold, underline, or italicize text, and you can select from three different colors for text or when you want to highlight words or sentences in a doc. You can also make comments on shared Word documents. When you're finished, just save to SkyDrive, and your document will have your changes and be available to edit from your other devices.
In Excel you can tap on cells and pinch to zoom, just like you would expect. If you want to jump to a specific chart or go between sheets, there's a button up top, which pulls up a useful outline view. Next to that are a Search tool, an AutoFilter toggle (for filtering a subset of data within a range of cells), and a Formula button, which gives you access to a few simple, often-used formulas.
Just as on a desktop, you can enter formulas for cells, and -- when you edit a cell -- the values will automatically update in your spreadsheet. You also can quickly create a chart of selected data by highlighting fields, hitting your Menu key, and touching Create Chart. You have six different chart types to choose from, and the app will automatically create the chart in a new tab.
With PowerPoint, you can't create a new presentation like you can for Word and Excel. Still, you can view previously made presentations, make small edits, hide slides, and view and edit speaker notes so you can practice a presentation on the go. The app has a button at the top for quick navigation to other slides, or you can swipe horizontally to navigate to the previous or next slide. To get a feel for your presentation, you also can switch to landscape mode and swipe to view your slides in full screen. You won't be able to create new slides or perform more-complex actions like adding transitions, but the app will still be useful for smaller edits before a big meeting. Also, it's worth noting that the app doesn't let you move slides around within your presentation, while the iOS version does.
So what's the problem?
Granted, we have only a couple of criticisms of Office Mobile, but they are big ones. The app is definitely useful for subscribers (and if you have an Office 365 subscription, why not download it?), but if you can access watered-down versions of Office for free online, it seems reasonable that you'd be able to do the same with this app with limited editing features. It would be better if the current version of the app were free and tied to the Web apps, with there also being a more robust version with more features tied to the Office 365 subscription. As is, it's giving you much less than you get for free in a Web browser, but you still have to subscribe to the service to use it. Fortunately, if you just want to check out the app, you can sign up for a free trial of Office 365 at Office.com. Once you're signed up, the Office Mobile app will work until the end of your trial period.
The other major problem is that Office Mobile is not compatible with Android tablets, which means that, for now, you're stuck with a small screen for editing and viewing your documents while on the go. With Android tablets unquestionably on the rise, it seems like a good idea to bring the power of Office to the relatively larger screen. Hopefully the folks at Microsoft are thinking in the same direction, and will soon make it happen.
Since this is just the first release of the app on Android, we're hoping that Microsoft will either add to Office Mobile or separate it into different downloadable versions. While Office Mobile doesn't give you a lot of features, it's definitely useful to subscribers for making quick edits on the go. That said, I think Microsoft could have captured a lot more hearts by making this app free to use without a subscription, and providing a more robust version for subscribers. And of course, tablet support would have been even better.