The Chrome beta channel has been updated to version 4. If you're already in the beta channel, you can go ahead and run the auto-update (if it hasn't ran already). If you're not in the beta channel, you can install the beta version from here: http://www.google.com/intl/en/landing/chrome/beta/
The big new feature in version 4 is Bookmarks Sync.
This is a feature that I have been waiting for in Chrome, since back when I used FireFox and IE I made heavy use of the synchronized bookmarks feature of the Google Toolbar. But with this new feature in Chrome, I was baffled that they synchronize the bookmarks to Google Docs rather than the Google Bookmarks service (which the toolbar has always used).
It makes sense when I think about it though. The folder that it creates in your Docs account is called "Google Chrome," and underneath that there is a "Bookmarks" folder. You could hide the Chrome folder if you want. I could see this becoming a central storage place for all of Chrome's settings, and possibly for future add-ons. Chrome OS may make good use of this folder as well.