Google Docs adds LaTeX support, customizable autocorrect
LaTeX is a fairly significant addition, since it should greatly improve Google Docs' spreadsheet muscle. While that alone won't pull it even with Excel, it's certainly a step in the right direction. Image insertion is as also a nice addition, and it's as simple as popping image=(URL) into a cell. You can also use Google Image search to insert files which are marked for re-use with modification.
Autocorrect is an extremely handy addition -- especially since you can use it for more than fixing up typographical errors. Google allows you to add your own corrections, so you can also use Docs autocorrect as a text expander -- to turn ffx into Firefox, for example. Pair autocorrect up with Google Scribe, and it won't be long before Google just types your whole doc for you.