Google has released two new apps for iOS, one for Docs and one for Sheets. The two apps are dedicated to viewing and editing text documents, as opposed to the Google Drive app, which shows all of your documents in one place. It's a way to easily find all of your documents of a single type. Both apps support all of the features that you would expect.
You can create new documents, edit existing ones, both online and off, and work collaboratively. Docs lets you add and respond to comments. Both apps function very much like the Google Drive app, including the ability to pin files for offline editing. However, unlike Drive for iOS, Docs and Sheets display all of your documents in the same view, including documents that have been shared with you by another user.
Google says that in addition to Docs and Sheets, a Google Slides app is on its way. You can download both universal apps from the App Store now.