Here's some usage data for Office for iPad
According to recent estimates by app tracking firm Destimo, of the 12 million downloads for Office so far, about 39% or 4,680,000 downloads are for Microsoft Word. Not too big of a surprise there. About 33% of downloads were for Excel or about 3,960,000 downloads. Lastly, about 29% of downloads or about 3,490,00 downloads were from PowerPoint. The revenue apportions are far more defined as to who is the winner. Microsoft Word accounted for well over half (55%) of revenues from all apps. Excel ran away with 32% of revenues and PowerPoint with a mere 12%. Personally, I thought PowerPoint would be the most popular on the iPad but, oh well. Some other nuggets: Of all American iOS app downloads from Office for iPad's launch on March 27th until April 2nd, Microsoft's Office apps accounted for 32%. More surprising, China accounted for 23% of downloads but only 2.7% of revenues. The United States, the United Kingdom, Germany, Australia and Canada contributed the most revenues in that order.
These are just some of the more interesting tidbits, but you can read the report in full for yourself here.
Here's a global breakdown of combined downloads from the apps:
And here's a global breakdown of all revenues from the apps: