Microsoft Office is finally available for the iPhone (not iPad yet). Unfortunately, it's so minimal that it looks like a botched attempt to bring some Office-like presence to the iPhone. I'd say a lot of other apps do a better job.
Apparently this is the first time you get to see Microsoft Office on the Mobile for iOS. The iPhone app is free but you'll need an Office 365 account to get started. If not, you are given an option to create the account from right within the app.
The Office Mobile includes:
Looks like these are the only three apps you can get within Office Mobile for iPhone. While you do get to open, edit and view documents of these formats easily, there are several unruly limitations to what you can produce. Considering that content creation on the iPhone isn't really great, the limited set of features that Office Mobile for iPhone provides just makes sense although it has drawn a lot of flak from reviewers.
Lacks a Few Useful Features
Office Mobile does not have a built-in spell-checker. It doesn't support a lot of fonts when you create documents but it does support all the fonts that come when you import/open a document. If you run Microsoft Office 2013 on your PC/Mac and are connected to Office 365, you can access your recent documents from within Office Mobile too. Basically, the cloud thing has been done right.
You don't have to be connected to a network to use Office Mobile. You can create and edit documents as you please and when you're connected to a network, the changes get synced to the cloud.
In the Cloud
As to cloud storage, when you sign-in with your Office 365 credentials, your SkyDrive storage gets linked automatically. But you can also add Sharepoint and other cloud accounts if you must.
Cloud is probably one reason why users might want to use this app but ultimately, it's only those with the Office 365 account that'd get to benefit from it. The rest of the users who don't have an Office 365: I don't think Microsoft can compel you to get that costly account just for Office Mobile. If you have iWork, you're much better and there are also other alternatives.