I've been using Office Mobile for iOS since its release, and it's simple and not overly powerful, but still useful. But it's also got an annoying bug that drives me up the wall. Read on for details.
The iOS version of Office is available for free for those who subscribe to Office 365. For $100 annually you can install Office on five devices, including iOS ones.
Office for iOS opens to your SkyDrive, and from there you can browse your folders and open and edit files. (Actually, you can't edit all of your files ... more on that later.) Tabs along the bottom of the screen make navigation quite useful. Tap icons to see only the most recent files you've opened in Office and saved to SkyDrive, browse your entire SkyDrive, create new files, or change your settings.
Given that you're viewing documents on a very small screen, they show up with reasonable fidelity to font size, formatting, and so on, including showing pictures where they've been placed. They won't look exactly as they do on your PC or laptop, because Office automatically reformats them for the small screen of the iPhone. That's what you want, because otherwise many documents would be unreadable. For wider documents, turn the iPhone sideways and the screen orientation changes. As an Office document viewer, it's superb.
You can edit files as well, and create new ones, although the editing tools are quite limited. For example, in Word, the font-handling leaves much to be desired. You'll be able to do the basics, such as changing font attributes such as bold and italic, or highlighting text. But you can't choose a specific font. And you can make text larger or smaller by tapping a + or ? button, but you can't set a specific font size. There's also no spell checker, undo command, or a way to add graphics.
PowerPoints is even more underpowered. You can rearrange your slides, edit text, and so on, but not much else. You also can't create a new PowerPoint presentation. Excel is a bit better, even letting you easily jump to different pages of a spreadsheet. But you won't be able to insert new rows and columns.
Commenting features throughout are limited, so you won't be able to review documents in the same way you can with full-blown Office. But there is a way to add comments to text or objects.
In short, it's not a powerhouse document creation or document editing tool. But I'm not convinced that it needs to be one on an iPhone. In theory, you can use it on an iPad, but because it's built for the small screen of the iPhone, the display leaves plenty to be desired.
Can't edit older files
If you've got files in older Office file formats, such as .doc, .xls, and .ppt, you'll be able to view the files, but not edit them. Office, though, doesn't make that clear. If you've opened one and try to edit it in Word, you get a message telling you that you can't edit files in the older format. But if you do the same thing in Excel, you only get a message saying "Can't edit workbook," with no explanation why. You may think the file corrupt, or in use by someone else, but in fact, it's just because Office for iOS can't edit older files.
And now for the bug
The suite has a bug that afflicts me, although I don't know whether anyone else has experienced it. In Office for iOS, I can't see all of my SkyDrive folders or open files contained in them. The files and folders are available from the Web, and synced to a variety of my Windows PCs and tablets. But they don't show up in the iOS version of Office. I tried saving files to one of those folders, hoping that it might show up in the Recent tab. But they don't show up there either.
If anyone out there has a fix, let me know, because I'm stymied. I'm hoping that one day it will magically fix itself. Stranger things have happened with computers.
For iPhone users who are Office 365 subscribers, it's a no-brainer: Download Office for iOS. Sure, it's got shortcomings (in particular if you want solid tools to edit files, and that oddball bug, at least on my iPhone), but it's a reasonably good piece of work.
If you're not already an Office 365 subscriber, it's unlikely that this app will turn you into one. There are Office alternatives out there that do more than Office on iOS, notably Polaris Office, Documents to Go Premium, and QuickOffice Pro, all of which cost about $15. So you won't way to pay $100 a year you'll have to pay for a subscription to Office 365, just to get your hands on the iOS version.