Yes, Google Docs is nearly unusable on the N800. If you zoom out (80%), and make sure the portion where you are writing is at the top (I add extra lines at bottom so I can scroll up), you can type a little.
Alternatively, you can use the full screen keyboard. If you are editing existing text, just highlight it before bringing the full screen keyboard up.
If I recall, It's usuability is marginal anyway as you loose the cursor position when it re-loads every minute or so. There was a google gears port for maemo, but Google Docs wouldn't recognize it. I lost it when upgrading to Diablo and haven't bothered to re-install.