Like most of the other apps in this roundup, ThinkFree is primarily designed for phones, but it works well on Android tablets too. The interface is clean and simple, even a little sparse, but easy enough to navigate. My one complaint on the menus is that the home tab offers no way to start a document or open an existing document; instead, you have to go to the My Docs, Online, or Google tabs. This strikes me as an oversight on ThinkFree's part, as it means you can't do much of anything that's worthwhile immediately upon launching the app.
ThinkFree falls short of getting a hearty recommendation from me because it crashed several times while accessing online services. Frequently, though not all the time, the app force-closed the moment I tapped the Google or Online tab. This happened exclusively on my Iconia tablet, and not on my HTC ThunderBolt phone.
Documents To Go
DataViz has been cranking out its Documents To Go mobile office suite for years, and the software remains one of the best document editors for smartphones. The latest update to the Android app brought some interface enhancements that tailored it a little better to Honeycomb tablets, giving it a distinct advantage over Google Docs and ThinkFree in its tablet interface.
Overall, however, despite its recent Honeycomb-friendly enhancements, the Documents To Go interface still feels like a small-screen UI stretched out to fill a larger display. With that said, Documents To Go is packed with useful context menus that give you just the options you need for the document you're working on, which makes it a good deal easier to work with than ThinkFree.
Documents To Go does an excellent job of handling Microsoft Office files from Word, Excel, and PowerPoint, and it includes the best Track Changes support I've seen on a mobile productivity app. It lets you store files locally, of course, but also syncs to your PC and accesses files stored on Google Docs with aplomb. Especially useful is the app's Starred Files feature, which makes it easy to mark important documents for quick retrieval later on.
For its rock-solid dependability and simple (though basic) context-sensitive interface, Documents To Go is tough to beat.
Quickoffice HD Pro (The Winner)
Only one app in this roundup has been designed specifically with Android tablets in mind, and that's Quickoffice HD Pro. The difference between a so-called HD app, fully designed for tablet displays, and a phone app that spreads out to fill a tablet screen is typically striking, and Quickoffice HD Pro is no exception. At $20, this app costs 33% more than its most serious competitors, but that extra $5 is chump change for the additional usability.