I think the most important new feature is the selective syncing. Now you can select which computers sync with which folders, so you don’t need to worry about saturating the wi-fi at your local coffee shop.
They’ve also made sure there will be no issues with metadata (such as in-app locking of files) syncing, which makes it more useful in a business environment. The client itself has been redone to be more efficient and use less RAM.
The 1.0 release is nicknamed “Rainbow Shell”.
The new version of Dropbox is available now, and should install right over your old version.