The biggest improvement is the new layout, which makes mobile document editing much easier and allows for collaboration from other Docs users. Currently, Google Docs supports devices with Android 2.2 (codename Froyo) and up, as well as Apple devices with iOS version 3.0 or newer. Unfortunately, Google doesn't specify if third-party browsers will work with the new Google Docs or whether it plans on adding new platforms such as Windows Phone and webOS.
The new functionality will be rolling out over the next few days to English-language users. To use it, just head over to docs.google.com with a compatible device. From there, create a new document or edit an existing one by just pressing the Edit button.