According to AndroidCentral, the downloading of the document or an app is not necessary, because "it's all done at docs.google.com from your Android browser. (Or iPhone and iPad, too.) And from there you can access all of your Google Docs."
TalkAndroid adds that "while this service will not allow you to edit your documents, let’s be honest — your phone isn’t the best device to do that, anyway. The viewer is very usable, though, and allows you to take your documents with you wherever you go."
Phandroid comments that the Android version of Google Docs doesn't seem to support "pinch to zoom at the moment, but document viewing is quick and easy to navigate."
Google also welcome feedback on the service by going to the Mobile Help Forum.
Image from Google Mobile Blog
Source: Google Mobile Blog