Google add-on plugins for Google Drive / Docs / Sheets

At Attacat we love Google Drive (or Docs as we still call it), and today it promises to get better with the launch of add-ons.

Edit: Add-ons don’t appear to be working yet, at least in the UK. The ‘Add-ons’ drop-down in the menu bar doesn’t appear, and clicking to access anything from the store just opens up a blank doc/sheet. Damn you Google!