Apple has just released a new version of Mac OS X to developers dubbed OS X Lion 10.7.3 Build 11d16. In this developer only update Apple is focusing on iCloud compatibility, with specific attention centered around iCloud document storage, Address Book, Mail and iCal. Another thing to keep in mind is that OS X Server 10.7.3 was also released to developers and it is meant to improve on the areas noted previously.
Note: Apple warns that you will not be able to revert back to your previous system after updating. Thus, please install this update on a system you are prepared to erase if necessary.
If you are interested in downloading Mac OS X Lion 10.7.3 or Mac OS X Server 10.7.3 you will need to login to your developer account.