It appears that hell has frozen over once again.
Of course, Microsoft also offers full-featured Office mobile apps for Windows Phone, Windows 8 and Windows RT. But the Android and iPhone versions, which offer nearly-identical functionality, are restricted to subscribers of Office 365, a service that costs $99 per year or $10 a month for the home version. (For back story on Office Mobile for iPhone, read "What You Need to Know About Microsoft's New Office App for iPhone.")
In other words: Microsoft isn’t giving away the keys to its (diminishing) kingdom. With Office Mobile for Android and iPhone, you can view and do some limited editing. You can create Word and Excel, but not PowerPoint, files. And to get the most out of the apps, you need to store your files in Microsoft’s SkyDrive or SkyDrive Pro cloud/file-sync service. (More about SkyDrive coming up.)
So how does the Android app work compared to the iOS version? Aside from some minor interface differences, the two apps are very similar. The main difference: Office Mobile is much easier to use on a larger screen than the iPhone's display, like the one found on my Samsung Galaxy Note.
Navigating through files in particular is much easier on a big-screen Android smartphone. I usually create a new file each time I open and edit a work-in-progress. Thumbing through those files in Office Mobile on my iPhone is tedious, because I can’t see the entire file name. Not so on my Galaxy Note. (See the screenshot below as an example. The iPhone screen is at left, Android at right).
But back to SkyDrive. One of my problems with the Office 365/SkyDrive ecosystem is SkyDrive doesn’t reliably sync files between my two Macs. That’s why, despite SkyDrive’s lower cost, I went back to Dropbox as my cloud-file-sync/sharing service of choice. It just works.
Unfortunately, Microsoft doesn’t offer in-app access to Dropbox files via Office Mobile. You can, however, click on a file in the Android Dropbox app and open it in Office Mobile for editing; the same’s true on an iPhone.
Another issue: Microsoft hasn't released tablet versions of Office Mobile for iOS or Android. The company wants tablet owners to use its free, SkyDrive-based Office Web Apps—which are also free if you stick within the 7GB storage limit.
So let’s recap: You can use Office Web Apps for free on a tablet, which is preferable (in my opinion) to working on smaller smartphone screens. And you can use Office Mobile on small-to-smallish smartphone screens, where it’s not as useful, but you have to pay for it.