For a year or so, you could put any document, presentation, image or file into your Google Docs account, but the viewers and tools were somewhat spotty.
More and more, Google Docs is becoming, literally, a more and more compelling "desktop" in the cloud. All your files will be there, with secure/easy sharing and easy-to-access compatibility across systems, devices, tablets, smartphones, etc.
The sidebar on the left has been refreshed with a smarter "home" view allowing you to filter in/out the things you want to see.
Folders and Labels are now called "Collections", which should make sorting and finding things easier.
There should also be improvements to search and filtering of files and I really hope refreshing speed improves as well!