Google acquired QuickOffice in June, and this is one of the first visible fruits of that acquisition. We've always been fans of Quickoffice as an iOS app suite, and figure it's worth the $8.49 price tag. Nonetheless, if you're already paying Google for Apps services, this is a nice bonus. Google says similar deals for the regular iOS and Android versions are "coming soon".
Quickoffice + Google Apps = better document conversion and an iPad app [Google Enterprise Blog]