Unless they've changed it in the last week or so, I know Docs to Go does NOT fully support external keyboards, and I **think** QuickOffice doesn't either. (Someone correct me if I'm wrong, it's been a couple of weeks.) However, all the note taking programs I've downloaded do support keyboards, oddly enough. Why a simple note app can handle it and D2G can't....?
I use Notebooks for the iPad to do all my writing at this point, because it does have pretty decent keyboard support, reads a variety of file types, and syncs to iDisk or other WebDAV services, plus I can wirelessly backup to my MBP. Pages doesn't export well, unfortunately, even to iDisk, let alone back to my computer. I'd gladly add D2G to my device, but the lack of support for something as basic as arrow keys is just nuts.