Disappointingly but unsurprisingly, Google Docs for Android doesn't do much of anything without a live data connection to Google Docs on the Web. While it's understandable that you can't open documents from your online Google Docs account without a connection, the fact that you can't cache documents for later editing or create new documents for later uploading makes it hard to think of this app as a full-featured editor. Offline editing, in my view, is a fundamental enough feature that its absence here seriously limits this app's usefulness.
What you actually get with Google Docs is an Android-friendly set of links to the Google Docs Web apps. The app itself is designed for phones, not tablets, so its six main buttons leave tons of empty space on the tablet screen. Once you're connected, however, the Google apps look good and play as nicely as you'd expect with the Android browser.
As I've documented elsewhere over the past few years, Google Docs has more than its share of compatibility issues with Microsoft Office document formats. It handily imports Office files for viewing and editing, and keeps simple files more or less intact, but saving those files as Office .docx, .xlsx, or .pptx files almost always introduces some sort of error in my experience. And if your document includes complex formatting that you'd like to preserve, you can pretty much count on disappointment.
If you're a Google Docs user on the Web, you should definitely download the free Google Docs app for Android, if only because it's the best app for that particular job. But if you're looking for a full-featured document editor with offline usability and great Microsoft Office compatibility, any of the other apps in this roundup will be a better choice.
ThinkFree Office Mobile
Despite its name, the full version of ThinkFree Office for Android is anything but free. It's $15, which puts it right in line with its offline-capable competitors in this roundup.
ThinkFree can read and write Microsoft Word, Excel, and PowerPoint formats, and it acts as a PDF viewer as well. It also includes integrated access to Google Docs, as well as access to ThinkFree Online, so you can use the Web-based apps when you're at a PC and the Android app when you're on the go. ThinkFree's Microsoft Office compatibility is solid, and I didn't encounter any noticeable formatting errors in the documents I sent back and forth between the Android app and Word, PowerPoint, and Excel. Even Excel charts looked as expected in ThinkFree.