Click the “Offline” link and you’ll see this pop-up:
After clicking “Enable offline access” you are given the choice to create a Google Apps icon/shortcut on the Desktop:
Click “Yes” to add the Desktop icon (unless you don’t want it) — I moved mine into Applications:
Google Gears will now start syncing all your Docs to your computer.
Once the status is “Synchronized,” test it out. Turn off your Airport or Ethernet connection and either double-click your Google Apps icon or open Safari and go to docs.google.com. It should pull up all your Docs just the way you remember, except for this prohibitory sign where the green check used to be:
Hovering your mouse over a file will tell you the last time it was synced (mouse pointer not pictured):
While everything seems to work perfectly, there are a few missing features (which I’m sure will be introduced soon). For example, you can only edit Documents offline, not Spreadsheets. You also can’t create new documents offline.