SQL Server 2008 Books Online: How to find out what features are in a CTP release
Whenever a CTP release is available it is best to refer to the documentation to know about the features that are available in this CTP are documented. In this case ensure you have downloaded the Books Online from that CTP release and open the BOL then go to 'What's New (component_name)' from Search option.
For example, the new T-SQL and database engine features available in this CTP are in the topic 'What's New (Database Engine).
The What's New topics will be updated with each CTP release.
Easy isn't it!